Fiber diameter measuring device, inorganic fiber sheet producing device, method for measuring fiber diameter, and method for producing inorganic fiber sheet

ABSTRACT

A fiber diameter measuring device, an inorganic fiber sheet producing device, a method for measuring a fiber diameter, and a method for producing an inorganic fiber sheet, capable of guaranteeing continuous safeness of the fiber diameter of an inorganic fiber in an inorganic fiber sheet is provided. A method further capable of measuring the fiber diameter of the inorganic fiber in the inorganic fiber sheet, not only after the production of the inorganic fiber sheet but also during the production of the inorganic fiber sheet is provided. The fiber diameter measuring device includes a sampling section capable of sampling a predetermined amount of the inorganic fiber in an entire area of the inorganic fiber sheet; and a measuring section configured to measure a fiber diameter of the sampled inorganic fiber.

TECHNICAL FIELD

The present disclosure relates to a fiber diameter measuring deviceconfigured to measure a fiber diameter of an inorganic fiber in aninorganic fiber sheet, an inorganic fiber sheet producing device usingthe same, a method for measuring a fiber diameter, and a method forproducing an inorganic fiber sheet.

BACKGROUND ART

Inorganic fiber moldings are widely used in applications such asindustrial insulation, refractories, and packing materials, wherein theyare exposed to high temperature conditions. In recent years, inorganicfiber moldings have also been used as cushioning materials forautomobile exhaust gas purifying devices, that is, holding materials forexhaust gas purifying devices which are wound around the exhaust gastreatment body when the exhaust gas treating body such as a catalystcarrier and a particle filter is housed in a metallic casing, and whichare interposed between the exhaust gas treating body and the casing.

However, ceramic fibers might cause health disorders such ascarcinogenicity, and regulations for inorganic fibers have beenstrengthened.

Examples of an indicator for safeness of an inorganic fiber molding mayinclude a fiber diameter of an inorganic fiber in an inorganic fibermolding. For example, the World Health Organization (WHO) defines afibrous material that is inhaled into the body with human respirationand reaches the lungs as “inhalable fiber” with a length more than 5 μm,a diameter less than 3 μm, and an aspect ratio (length to diameterratio) more than 3.

When measuring a fiber diameter of an inorganic fiber in a sheet-shapedinorganic fiber molding (inorganic fiber sheet), the following method isgenerally carried out; a method wherein a part of an inorganic fibersheet is punched out or cut out to collect a test piece having apredetermined size, and a fiber diameter of an inorganic fiber in thetest piece is measured (see, for example, Non-patent Literature 1). Theabove process is based on an assumption that, when the productionconditions of the inorganic fiber sheet are constant, the average fiberdiameter and the fiber diameter distribution, for example, of theinorganic fiber sheet will be the same. However, in the above method, itcannot be said that the reliability of the fiber diameter is guaranteedwith respect to the lot or the potion that is not measured. Therefore,there is a need for a measuring method that guarantees continuity anduniformity of average fiber diameter and fiber diameter distribution,for example, in the entire area of the inorganic fiber sheet, in otherwords, a method that guarantees the safeness of the fiber diameter inthe entire area of the inorganic fiber sheet, that is, a method thatguarantees the continuous safeness of the fiber diameter in theinorganic fiber in an inorganic fiber sheet.

Also, in the above method, since a part of the inorganic fiber sheet ispunched out or cut out for sampling, the inorganic fiber sheet aftersampling cannot be used as a product.

Further, the above method is a method wherein the fiber diameter ismeasured off-line after the production of an inorganic fiber sheet, andit is not possible to measure the fiber diameter on-line duringproduction of a inorganic fiber sheet. Particularly, in a case of alengthy inorganic fiber sheet, only the fiber diameter of the punchedout or cut out part as a test piece may be confirmed by the off-linemethod. Therefore, a method wherein the fiber diameter is measured forthe entire width and the entire length of the lengthy inorganic fibersheet, is important.

CITATION LIST Non-Patent Literature

Non-patent Literature 1: COMMISSION REGULATION (EC) No. 761/2009 of 23Jul. 2009

SUMMARY OF DISCLOSURE Technical Problem

In response to such problems, the present inventors have studied amethod wherein, in measuring a fiber diameter, reliability of the fiberdiameter may be guaranteed, and an object may be used as a product evenafter measurement of a fiber diameter, and further, a fiber diameter maybe measured on-line during production of an inorganic fiber sheet,rather than offline as described above. However, effective methods forsuch methods have not yet been established.

The present disclosure has been made in view of the above circumstances,and a main object of the present disclosure is to provide a fiberdiameter measuring device, an inorganic fiber sheet producing device, amethod for measuring a fiber diameter, and a method for producing aninorganic fiber sheet capable of guaranteeing continuity and uniformityof the fiber diameter of an inorganic fiber in an inorganic fiber sheet;also, capable of guaranteeing continuous safeness of the fiber diameterof an inorganic fiber in an inorganic fiber sheet; and further, capableof measuring the fiber diameter of the inorganic fiber in the inorganicfiber sheet, not only after the production of the inorganic fiber sheetbut also during the production of the inorganic fiber sheet.

Solution to Problem

In order to achieve the object, the present disclosure provides a fiberdiameter measuring device configured to measure a fiber diameter of aninorganic fiber in an inorganic fiber sheet including the inorganicfiber, the device comprising, a sampling section capable of sampling apredetermined amount of the inorganic fiber in an entire area of theinorganic fiber sheet; and a measuring section configured to measure afiber diameter of the sampled inorganic fiber, and as necessary, thesampling section includes a sample transferring section configured totransfer the inorganic fiber, a pretreating section configured to assistthe sampling of the inorganic fiber, and a sample collecting sectionconfigured to collect the

According to the present disclosure, since a predetermined amount of theinorganic fiber may be sampled in the entire area of the inorganic fibersheet in the sampling section, the sampled inorganic fiber may beregarded as representing the inorganic fiber in the inorganic fibersheet. Therefore, it is possible to improve the reliability of the fiberdiameter of the measured inorganic fiber. Also, in sampling section,since the inorganic fiber sheet is not punched out or cut out forsampling, the fiber diameter of the inorganic fiber in the inorganicfiber sheet may be measured on-line. Still more, since the appearance ofthe inorganic fiber sheet may be suppressed from being impaired bymeasurement of the fiber diameter, the inorganic fiber sheet may be usedas a product even after measurement of the fiber diameter.

In the present disclosure, the sampling section may include a sampletransferring section placed on one side or both sides of the inorganicfiber sheet, and configured to transfer the inorganic fiber. In thiscase, the sample transferring section may be a suctioning sectionconfigured to suction the inorganic fiber.

Also, in the present disclosure, the sampling section may include apretreating section configured to assist the sampling of the inorganicfiber. In this case, the pretreating section may be a physicallycontactless section configured to be physically contactless with theinorganic fiber sheet. Also, in this case, the physically contactlesssection may be a feeding section configured to feed a gas or a liquid tothe inorganic fiber sheet, from one side or both sides of the inorganicfiber sheet. Also, the pretreating section may be a physicallycontacting section configured to be in physically contact with theinorganic fiber sheet.

Also, in the present disclosure, as the pretreating section, thesampling section may include a vibration section configured to impart avibration to the inorganic fiber sheet.

Also, in the present disclosure, the sampling section may include asample collecting section configured to collect the inorganic fiber.

The present disclosure also provides an inorganic fiber sheet producingdevice comprising the fiber diameter measuring device described above.

According to the present disclosure, by comprising the fiber diametermeasuring device described above, it is possible to improve thereliability of the fiber diameter of the measured inorganic fiber. Also,by comprising the fiber diameter measuring device described above, thefiber diameter of the inorganic fiber in the inorganic fiber sheet maybe measured on-line. Still more, variation of the fiber diameter of theinorganic fiber and deviation from acceptable range may be checkedon-line. Therefore, by feeding the result back to the productionprocess, for example, of the inorganic fiber sheet, and controlling theproduction conditions, for example, of the inorganic fiber sheet, thefiber diameter of the inorganic fiber may be kept in a predeterminedstandard range. Also, by comprising the fiber diameter measuring devicedescribed above, an inorganic fiber sheet with good appearance evenafter the measurement of the fiber diameter may be obtained.

In the inorganic fiber sheet producing device in the present disclosure,a burning section configured to burn an inorganic fiber precursor sheetincluding an inorganic fiber precursor continuously, is preferablyprovided on an upstream side of the fiber diameter measuring device.This is because the present disclosure is useful for producing a lengthyinorganic fiber sheet.

The present disclosure also provides a method for measuring a fiberdiameter measuring a fiber diameter of an inorganic fiber in aninorganic fiber sheet including the inorganic fiber, the methodcomprising, a sampling step of sampling the inorganic fiber from theinorganic fiber sheet by a sampling method capable of sampling apredetermined amount of the inorganic fiber in an entire area of theinorganic fiber sheet; and a measuring step of measuring the fiberdiameter of the sampled inorganic fiber.

According to the present disclosure, since a predetermined amount of theinorganic fiber may be sampled in the entire area of the inorganic fibersheet in the sampling step, it is possible to improve the reliability ofthe fiber diameter of the measured inorganic fiber. Also, since theinorganic fiber sheet is not punched out or cut out for sampling, thefiber diameter of the inorganic fiber in the inorganic fiber sheet maybe measured on-line. Still more, since the appearance of the inorganicfiber sheet may be suppressed from being impaired by measurement of thefiber diameter, the inorganic fiber sheet may be used as a product evenafter measurement of the fiber diameter.

In the present disclosure, in the sampling step, the inorganic fiber maybe transferred by a sample transferring section placed on one side orboth sides of the inorganic fiber sheet, and configured to transfer theinorganic fiber. Also, in the present disclosure, in the sampling step,the sampling of the inorganic fiber may be assisted by a pretreatingsection configured to assist the sampling of the inorganic fiber.

The present disclosure further provides a method for producing aninorganic fiber sheet, the method comprising, a sampling step ofsampling an inorganic fiber from an inorganic fiber sheet by a samplingmethod capable of sampling a predetermined amount of the inorganic fiberin an entire area of the inorganic fiber sheet including the inorganicfiber; and a measuring step of measuring the fiber diameter of thesampled inorganic fiber.

According to the present disclosure, since a predetermined amount of theinorganic fiber may be sampled in the entire area of the inorganic fibersheet in sampling step, it is possible to improve the reliability of thefiber diameter of the measured inorganic fiber. Also, since theinorganic fiber sheet is not punched out or cut out for sampling, thefiber diameter of the inorganic fiber in the inorganic fiber sheet maybe measured on-line. Also, an inorganic fiber sheet with good appearanceeven after the measurement of the fiber diameter may be obtained.

In the present disclosure, in the sampling step, the inorganic fiber maybe transferred by a sample transferring section placed on one side orboth sides of the inorganic fiber sheet, and configured to transfer theinorganic fiber. Also, in the present disclosure, in the sampling step,the sampling of the inorganic fiber may be assisted by a pretreatingsection configured to assist the sampling of the inorganic fiber.

Also, prior to the sampling step, the method for producing an inorganicfiber sheet in the present disclosure preferably comprises a preparingstep of preparing an inorganic fiber precursor sheet including aninorganic fiber precursor; and a burning step of burning the inorganicfiber precursor sheet continuously to obtain the inorganic fiber sheet.This is because the present disclosure is useful for producing a lengthyinorganic fiber sheet.

Also, in the present disclosure, when the fiber diameter measured in themeasuring step is out of a previously set predetermined range, a resultthereof may be fed back, and a producing condition of the inorganicfiber precursor sheet and/or a burning condition in the burning step maybe controlled so that the fiber diameter is in the predetermined range.Variation of the fiber diameter of the inorganic fiber and deviationfrom acceptable range may be checked on-line. Therefore, by feeding theresult back, and controlling the producing conditions of the inorganicfiber precursor sheet, and/or he burning conditions in the burning step,the fiber diameter of the inorganic fiber may be kept in an acceptablerange.

Also, in the present disclosure, the inorganic fiber sheet subjected tothe sampling step is preferably an inorganic fiber sheet subjected to aneedling treatment. This is because the present disclosure is useful forthe inorganic fiber sheet subjected to a needling treatment.

Advantageous Effects of Disclosure

The present disclosure exhibits effects of being capable of guaranteeingcontinuity and uniformity of the fiber diameter of an inorganic fiber inan inorganic fiber sheet; also, capable of guaranteeing continuoussafeness of the fiber diameter of an inorganic fiber in an inorganicfiber sheet; and further, capable of measuring the fiber diameter of theinorganic fiber in the inorganic fiber sheet, not only after theproduction of the inorganic fiber sheet but also during the productionof the inorganic fiber sheet.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view illustrating an example of a fiber diametermeasuring device in the present disclosure.

FIG. 2 is a schematic view illustrating another example of a fiberdiameter measuring device in the present disclosure.

FIG. 3 is a schematic view illustrating another example of a fiberdiameter measuring device in the present disclosure.

FIG. 4 is a schematic view illustrating an example of an inorganic fibersheet producing device in the present disclosure.

FIG. 5 is an average fiber diameter distribution diagram in Example andReference Examples.

DESCRIPTION OF EMBODIMENTS

The fiber diameter measuring device, the inorganic fiber sheet producingdevice, the method for measuring a fiber diameter, and the method forproducing an inorganic fiber sheet in the present disclosure arehereinafter explained.

A. Fiber Diameter Measuring Device

Firstly, the fiber diameter measuring device in the present disclosureis explained. The fiber diameter measuring device in the presentdisclosure is configured to measure a fiber diameter of an inorganicfiber in an inorganic fiber sheet including the inorganic fiber, thedevice comprising, a sampling section capable of sampling apredetermined amount of the inorganic fiber in an entire area of theinorganic fiber sheet; and a measuring section configured to measure afiber diameter of the sampled inorganic fiber.

Here, the phrase “an entire area of the inorganic fiber sheet” refers tothe bare minimum area required for sampling a fiber diameter measuringsample representing the entire inorganic fiber sheet, and refers to theentire area in the in-plane direction of an inorganic fiber sheet, andis preferably the entire area in the in-plane direction and thethickness direction of an inorganic fiber sheet.

In the present disclosure, a fiber diameter measuring samplerepresenting the entire inorganic fiber sheet is collected by carryingout a sampling from one side or both sides of the inorganic fiber sheetby the sampling section as described later. Whether the sampling of theinorganic fiber by the sampling section is carried out from one side ofthe inorganic fiber sheet, or from both sides of the inorganic fibersheet may be appropriately selected according to method for producingthe inorganic fiber sheet, particularly to the inorganic fiber precursorsheet used for producing the inorganic fiber sheet.

Specifically, the inorganic fiber precursor forming the inorganic fiberprecursor sheet is formed via a spinning step such as a blowing methodand a spinning method. And in a case of a producing method wherein eachof the inorganic fiber precursors are present as random in the thicknessdirection when an inorganic fiber precursor sheet is formed, the sampledinorganic fiber may be regarded as sufficiently representing theinorganic fiber sheet of the entire inorganic fiber sheet, even when thesampling section is placed only on one side of the inorganic fibersheet. Therefore, it is also possible to place the sampling section onlyon one side of the inorganic fiber sheet. Incidentally, the spuninorganic fiber precursors being present as random in the thicknessdirection of the inorganic fiber precursor sheet, means that theinorganic fiber precursor, discharged from a certain spinning nozzle inthe spinning step, is present at a probability density which is equallydispersed at any location in the in-plane direction and in the thicknessdirection of the inorganic fiber precursor sheet, without being alwayspresent at a certain location of the inorganic fiber precursor sheet.

Incidentally, when the inorganic fiber precursor is dispersed at equalprobability in the thickness direction of the inorganic fiber precursorsheet, but the inorganic fiber precursor is not dispersed at equalprobability in the in-plain direction of the inorganic fiber precursorsheet, it cannot be regarded as random. However, the collected fiberdiameter measuring sample may be regarded as representing the entireinorganic fiber sheet, by carrying out the sampling of the inorganicfiber in the entire area in the in-plain direction of the inorganicfiber sheet with the sampling section, even when the sampling section isplaced only on one side of the inorganic fiber sheet. Therefore, it isalso possible to employ an aspect wherein the sampling section is placedonly on one side of the inorganic fiber sheet.

Examples of the producing method wherein the spun inorganic fiberprecursor is present as random in the thickness direction of theinorganic fiber precursor sheet, may include a producing method whereina sheet-shape is formed after going through stacking by, for example,zigzag folding; and a producing method wherein the inorganic fiberprecursor is stirred so as to be completely random, and then, stacked toform a sheet-shape.

Among them, when the sampled inorganic fiber shows the fiber diametermeasurement result which may be regarded as representing the inorganicfiber sheet in the actual aspect wherein the sampling section is placedonly on one side of the inorganic fiber sheet, it is preferable toemploy the aspect wherein the sampling section is placed only on oneside of the inorganic fiber sheet.

As described in the evaluation of the Example and Reference Examplesbelow, representing in this case means that, when compared with themeasurement sample prepared or adjusted from an inorganic fiber sheet bythe conventional Die-cutting (preferably complying with COMMISSIONREGULATION (EC) No. 761/2009 of 23 Jul. 2009) (hereinafter sometimesreferred to as a conventional method fiber), the average fiber diameterof the inorganic fiber sampled in the actual aspect wherein the samplingsection is placed only on one side of the inorganic fiber sheet(hereinafter sometimes referred to as a sampling method fiber) is in therange of the variation of the conventional method fiber (which may be avariation in the average fiber diameter of each of the divided inorganicfiber sheet prepared or adjusted after dividing the inorganic fibersheet into a constant area, as in the Reference Example describedbelow). This variation is preferably within ±3σ of the average value,more preferably within ±2σ of the average value, and more preferablywithin ±σ of the average value, when the standard deviation is regardedas σ (sigma), when the probability density distribution of the variationof the fiber diameter or the average fiber diameter of the conventionalmethod fiber is a normal distribution. Similarly, in the case where theprobability density distribution of the variation of the fiber diameteror the average fiber diameter of the conventional method fiber is not anormal distribution, it is preferable that the average fiber diameter ofthe sampling method fiber is present within 49.85% on each of the thickside and the thin side from the center (average value) of the existenceprobability of the fiber diameter or the average fiber diameter of theconventional method fiber, further preferably present within 47.70%, andmore preferably present within 34.15%.

Meanwhile, when each of the inorganic fiber precursors are not presentas random in the in-plane direction and in the thickness direction ofthe inorganic fiber precursor sheet when an inorganic fiber precursorsheet is formed, and the inorganic fiber precursors discharged from aspecific spinning nozzle are present at a certain location of theinorganic fiber precursor sheet certainly or at high probability, thesampled inorganic fiber may be regarded as sufficiently representing theinorganic fiber sheet of the entire inorganic fiber sheet by placing thesampling section on both sides of the inorganic fiber sheet. Therefore,it is preferable to place the sampling section on both sides of theinorganic fiber sheet. Incidentally, when the inorganic fiber precursoris dispersed at equal probability in the in-plain direction of theinorganic fiber precursor sheet, but the inorganic fiber precursor isnot dispersed at equal probability in the thickness direction of theinorganic fiber precursor sheet, there may be a case wherein the sampledfiber diameter measuring sample cannot be regarded as representing theentire inorganic fiber sheet, particularly unless the sampling sectionsare placed on both sides of the inorganic fiber sheet. Therefore, inthis case, it is preferable to place the sampling sections on both sidesof the inorganic fiber sheet, and collect the inorganic fiber from bothsides of the inorganic fiber sheet.

However, this does not apply when the thickness of the inorganic fibersheet is extremely thin, and the inorganic fiber representing theinorganic fiber sheet may be obtained without being affected by the biasof the probability density by going through a pretreating sectionconfigured to assist the sampling of the inorganic fiber. The casewherein the thickness of the inorganic fiber sheet is extremely thin,and the inorganic fiber representing the inorganic fiber sheet may beobtained without being affected by the bias of the probability densityby going through a pretreating section configured to assist the samplingof the inorganic fiber, indicates a case wherein the sampled inorganicfiber shows the fiber diameter measurement result which may be regardedas representing the inorganic fiber sheet in the actual aspect whereinthe sampling section is placed only on one side of the inorganic fibersheet. The judging criterion for determining whether a fiber diametermeasurement result may be regarded as representing the inorganic fibersheet, or not is determined based on whether the variation is in therange similar to a case of determining whether the sampling section maybe placed only on one side of the inorganic fiber sheet, or not in thesampling section described above, and the details thereof have beendescribed above.

Also, for example, when a predetermined region of an end portion in awidth direction of an inorganic fiber sheet is trimmed, the “entire areaof the inorganic fiber sheet” includes an aspect wherein the entireregion of the inorganic fiber sheet is an entire region of the inorganicfiber sheet after being trimmed.

A fiber diameter measuring device in the present disclosure areexplained with reference to drawings. Incidentally, in the presentdescriptions, the same reference sign is indicated for the same factorin in description of the drawings, and duplicated explanation may beomitted in some cases.

FIG. 1 is a schematic diagram illustrating an example of the fiberdiameter measuring device in the present disclosure. Fiber diametermeasuring device 10 illustrated in FIG. 1 is an example of a fiberdiameter measuring device configured to measure a fiber diameter of aninorganic fiber in a lengthy inorganic fiber sheet 1. As illustrated inFIG. 1 , fiber diameter measuring device 10 comprises sampling section 2capable of sampling a predetermined amount of the inorganic fiber in anentire area of the inorganic fiber sheet 1; and measuring section 3configured to measure a fiber diameter of the sampled inorganic fiber.In the example illustrated in FIG. 1 , the sampling section 2 is placedon the lower side of the inorganic fiber sheet 1. However, thearrangement of the sampling section 2 is not limited thereto, and may beplaced on the upper side of the inorganic fiber sheet 1.

In the fiber diameter measuring device 10 illustrated in FIG. 1 , thelengthy inorganic fiber sheet 1 is conveyed by conveyance rolls 11 and12. Firstly, the sampling section 2 includes sample collecting section 2c such as a container having an upper opening, configured to collect theinorganic fiber from the lower side of the inorganic fiber sheet 1. Atthis time, the sampling section 2 preferably includes sampletransferring section 2 a configure to transfer the inorganic fiber inorder to increase the amount of the inorganic fiber collected per unittime. Examples of the sample transferring section 2 a may include, aswill be described later, a suctioning section and a physical conveyancesection. Among them, the suctioning section is preferable as the sampletransferring section 2 a because of its simplicity.

Hereinafter, in the fiber diameter measuring device 10 illustrated inFIG. 1 , a case where the sampling section 2 includes a suctioningsection as the sample transferring section 2 a, and sample collectingsection 2 c is described.

In this case, in an area wherein the suctioning port of the sampletransferring section 2 a (suctioning section) is in contact with orproximity to the inorganic fiber sheet 1, inorganic fiber sample may beefficiently transferred from the inorganic fiber sheet 1 to the samplecollecting section 2 c. As the result, the inorganic fiber may beefficiently collected. Therefore, for example, by setting the width ofthe suctioning port of the sample transferring section 2 a (suctioningsection) to be equal to or larger than the width of the inorganic fibersheet 1, or by transferring the sample transferring section 2 a(suctioning section) relative to the inorganic fiber sheet 1, apredetermined amount of the inorganic fiber may be collected in theentire area of the inorganic fiber sheet 1.

Also, in the sample transferring section 2 a (suctioning section), theinorganic fiber is collected by suctioning the inorganic fiber from theinorganic fiber sheet 1. Since it is not necessary to punch out or cutout the inorganic fiber sheet 1 for the sampling, the appearance of theinorganic fiber sheet 1 may be suppressed from being impaired. Then, thefiber diameter of the sampled inorganic fiber is measured by themeasuring section 3. In the measuring section 3, the average fiberdiameter, and fiber diameter distribution, for example, of the inorganicfiber diameter may be measured. It is preferable to use an automatedfiber diameter measuring device as the measuring section 3 since it iseasy to continuously acquire the measurement results.

Also, in the fiber diameter measuring device in the present disclosure,the sampling section 2 preferably includes a pretreating sectionconfigured to assist the sampling of the inorganic fiber. Examples ofthe pretreating section may include a physically contactless section anda physical contacting section, as described below. Examples of thephysically contactless section may include, as will be described later,a feeding section configured to feed a gas or a liquid to the inorganicfiber sheet, and a section configured to impart a vibration to theinorganic fiber sheet itself by feeding air, for example,intermittently. Examples of the physically contacting section mayinclude, as will be described later, a section configured to bring aplate-shaped material, a brush-shaped material and a comb-shapedmaterial into contact with the inorganic fiber sheet surfacesubstantially horizontally; a section configured to pick the inorganicfiber up from the inorganic fiber sheet by a picking tool; and a sectionconfigured to vibrate a site in contact with the inorganic fiber sheetduring conveyance. Among them, the feeding section and the vibrationsection are preferable as the pretreating section, as will be describedlater.

Hereinafter, a case where the sampling section includes a feedingsection as the pretreating section, a sample collecting section, and asample transferring section is described referring to FIG. 2 . Also, acase where the sampling section includes a vibration section as thepretreating section, and a sample collecting section is describedreferring to FIG. 3 .

FIG. 2 is a schematic view illustrating another example of the fiberdiameter measuring device in the present disclosure. In the exampleillustrated in FIG. 2 , as the pretreating section, the sampling section2 includes feeding section 2 b configured to feed a gas such as air or aliquid such as water, to the inorganic fiber sheet 1, from the upperside of the inorganic fiber sheet 1, and further includes sampletransferring section 2 a configured to transfer the inorganic fiberincluded in the gas or the liquid, from the lower side of the inorganicfiber sheet 1, and sample collecting section 2 c. In the exampleillustrated in FIG. 2 , the sample transferring section 2 a and thesample collecting section 2 c are placed on the opposite side of thefeeding section 2 b. However, the arrangement of the sample transferringsection 2 a and the sample collecting section 2 c is not limitedthereto, and may be placed, for example, immediately after the feedingsection 2 b.

In the fiber diameter measuring device 10 illustrated in FIG. 2 ,firstly, a gas or liquid is fed from the upper side of the inorganicfiber sheet 1 by the feeding section 2 b, so that the gas or the liquidis passed through in the thickness direction of the inorganic fibersheet 1, and the gas or the liquid including the inorganic fiber iscollected from the lower side of the inorganic fiber sheet 1 by thesample transferring section 2 a and the sample collecting section 2 c.As the result, the inorganic fiber is collected. At this time, theinorganic fiber may be collected from the inorganic fiber sheet 1 in thearea where the gas or the liquid is fed to the inorganic fiber sheet 1.Therefore, for example, a predetermined amount of the inorganic fibermay be collected in the entire area of the inorganic fiber sheet 1 byfeeding the gas or the liquid in the entire area in the width directionof the inorganic fiber sheet 1 by the feeding section 2 b. Also, in thefeeding section 2 b, sample transferring section 2 a, and samplecollecting section 2 c, the inorganic fiber is collected by passing thegas or liquid in the thickness direction of the inorganic fiber sheet 1,and it is not necessary to punch out or cut out the inorganic fibersheet 1 for sampling, so that the appearance of the inorganic fibersheet 1 may be suppressed from being impaired. The fiber diameter of thesampled inorganic fiber is then measured by the measuring section 3.

FIG. 3 is a schematic view illustrating another example of the fiberdiameter measuring device in the present disclosure. In the exampleillustrated in FIG. 3 , as the pretreating section, the sampling section2 includes vibration section 2 d placed on the lower side of theinorganic fiber sheet 1 that is configured to impart a vibration to theinorganic fiber sheet 1; and further includes sample collecting section2 c placed on the lower side of the inorganic fiber sheet 1 that isconfigured to collect the inorganic fiber sample dropped by thevibration. In the example illustrated in FIG. 3 , the vibration section2 d is placed on the lower side of the inorganic fiber sheet 1. However,the arrangement of the vibration section 2 d is not limited thereto, andmay be placed on the upper side of the inorganic fiber sheet 1.

In the fiber diameter measuring device 10 illustrated in FIG. 3 ,firstly, a vibration is imparted to the inorganic fiber sheet 1 by thevibration section 2 d, and the inorganic fiber dropped by the vibrationis obtained by the sample collecting section 2 c. At this time, theinorganic fiber may be collected from the inorganic fiber sheet 1 in thearea where the vibration is imparted to the inorganic fiber sheet 1.Therefore, for example, a predetermined amount of the inorganic fibermay be collected in the entire area of the inorganic fiber sheet 1 byimparting the vibration to the entire area in the width direction of theinorganic fiber sheet 1 by the vibration section 2 d. Also, thevibration section 2 d and the sample collecting section 2 c collect theinorganic fiber by imparting the vibration to the inorganic fiber sheet1, and it is not necessary to punch out or cut out lthe inorganic fibersheet 1 for sampling, so that the appearance of the inorganic fibersheet 1 may be suppressed from being impaired. The fiber diameter of thesampled inorganic fiber is then measured by the measuring section 3.Also, in the fiber diameter measuring device 10 illustrated in FIG. 3 ,the sampling section 2 may include the sample transferring section.

Incidentally, FIGS. 1 to 3 illustrate examples of the fiber diametermeasuring device configured to measure the fiber diameter of theinorganic fiber in the lengthy inorganic fiber sheet 1. However, thefiber diameter measuring device in the present disclosure may be a fiberdiameter measuring device configured to measure the fiber diameter ofthe inorganic fiber in a single sheet shaped inorganic fiber sheet.

According to the present disclosure, since a predetermined amount of theinorganic fiber may be sampled in the entire area of the inorganic fibersheet in sampling section, the sampled inorganic fiber may be regardedas representing the inorganic fiber in the inorganic fiber sheet.Therefore, by using the fiber diameter measuring device in the presentdisclosure, it is capable of guaranteeing continuous safeness of thefiber diameter of an inorganic fiber in an inorganic fiber sheet, and itis possible to improve the reliability of the average fiber diameter andthe fiber diameter distribution, for example, of the measured inorganicfiber. For example, in a case of a lengthy inorganic fiber sheet, it ispossible to guarantee the average fiber diameter and the fiber diameterdistribution, for example, of the inorganic fiber in the entire area ofthe sheet. Therefore, a safer inorganic fiber sheet may be provided.

Also, according to the present disclosure, since the sampling section isa section capable of sampling a predetermined amount of the inorganicfiber in the entire area of the inorganic fiber sheet, the fiberdiameter of the inorganic fiber in the inorganic fiber sheet may bemeasured without punching out or cutting out the inorganic fiber sheetfor sampling. Therefore, the fiber diameter of the inorganic fiber inthe inorganic fiber sheet may be measured, not only after the productionof the inorganic fiber sheet but also during the production of theinorganic fiber sheet. That is, the fiber diameter of the inorganicfiber in the inorganic fiber sheet may be measured on-line. Therefore,the average fiber diameter and the fiber diameter distribution, forexample, of the inorganic fiber in the inorganic fiber sheet may becontrolled on-line. The variation of the average fiber diameter and thefiber diameter distribution, for example, of the inorganic fiber anddeviation from acceptable range may also be checked on-line. Therefore,by feeding the result back to the production process, for example, ofthe inorganic fiber sheet, and controlling the production conditions ofthe inorganic fiber sheet, the average fiber diameter and the fiberdiameter distribution, for example, of the inorganic fiber may be keptin an acceptable range.

According to the present disclosure, since the sampling section is asection wherein a predetermined amount of the inorganic fiber may besampled in the entire area of the inorganic fiber sheet, and since theinorganic fiber sheet is not punched out or cut out, the physicalproperties and the appearance of the inorganic fiber sheet used for themeasuring may be suppressed from being greatly impaired. For example,when measuring the fiber diameter of an inorganic fiber in an inorganicfiber sheet subjected to a needling treatment, it is particularlyimportant that the inorganic fiber sheet subjected to a needlingtreatment does not defect the vertical bundles composed of the inorganicfibers, since the vertical bundles composed of the inorganic fibersconfigured to bind short fibers in the thickness direction play asignificant role in ensuring the physical properties and appearance. Byusing the fiber diameter measuring device in the present disclosure, aninorganic fiber sheet having good physical properties and appearanceeven after the measurement of the fiber diameter may be obtained, and itmay be used as a product as it is.

Hereinafter, the inorganic fiber sheet in the present disclosure andeach constitution of the fiber diameter measuring device in the presentdisclosure will be described.

1. Inorganic Fiber Sheet

The inorganic fiber sheet in the present disclosure includes aninorganic fiber. The inorganic fiber sheet is referred to as, forexample, a mat or a blanket.

The inorganic fiber constituting the inorganic fiber sheet is notparticularly limited, and, for example, one or more selected fromalumina fiber, ceramic fiber, biosoluble fiber (alkaline earth silicatefiber), rock wool, basalt fiber, potassium titanate fiber, calciumsilicate fiber and glass fiber, may be used. The inorganic fiber ispreferably one or more selected from alumina fiber, ceramic fiber,biosoluble fiber (alkaline earth silicate fiber), and basalt fiber.Also, examples of the inorganic fiber may include a simplex or complexfiber such as silica, alumina/silica, and zirconia, spinel, titania andcalcia including these. Among them, alumina/silica fiber includingalumina and silica as main components is preferable, and particularlypreferably a crystalline alumina/silica fiber. Although the ratio ofaluminum and silicon is not particularly limited, the ratio ispreferably in a range of 60:40 to 98:2, more preferably in a range of65:35 to 95:5, and particularly preferably in a range of 70:30 to 80:20,converted to Al₂O₃/SiO₂ mass ratio.

The inorganic fiber is preferably a short fiber. This is because thetoughness may be enhanced without impairing the thickness of theinorganic fiber sheet. Also, when the inorganic fiber is a short fiber,safety may be a problem.

Incidentally, the inorganic fiber being a short fiber means, forexample, that the average fiber length of the inorganic fiber is 1000 mmor less. Also, when the inorganic fiber is a short fiber, the averagefiber length of the inorganic fiber may be in a range of, for example,210 μm or more and 1000 μm or less.

The average fiber diameter of the inorganic fiber is not particularlylimited, and is preferably, for example, 3 μm or more and 15 μm or less,more preferably 4 μm or more and 13 μm or less, further preferably 5 μmor more and 10 μm or less, and particularly preferably 5 μm or more and8 μm or less. This is because the repulsive force and toughness of theinorganic fiber are improved, and the strength of the fiber may beincreased. Incidentally, when the average fiber diameter of theinorganic fiber is too long, the normal temperature compressive cyclingproperty (cold compression) of the inorganic fiber sheet is lost, andmeanwhile, when the average fiber diameter is too short, the amount offibrous material that reaches the lung when inhaled might be increased.

The inorganic fiber sheet is preferably subjected to a needlingtreatment. As described above, in the inorganic fiber sheet subjected toa needling treatment, particularly, since the vertical bundles composedof the inorganic fibers configured to bind fibers in the thicknessdirection play a significant role in ensuring the physical propertiesand appearance, it is important that the vertical bundles composed ofthe inorganic fibers are not defected. Since the physical properties andthe appearance of the inorganic fiber sheet used for the measuring maybe suppressed from being greatly impaired, the present disclosure isuseful for measuring the fiber diameter of the inorganic fiber sheetsubjected to a needling treatment.

The inorganic fiber sheet subjected to a needling treatment has aplurality of needle marks, that is, a plurality of recesses. The needlemark may be a through hole which penetrates through in the thicknessdirection of the inorganic fiber sheet, and may be a non-through holewhich does not penetrate through the sheet.

The number of the needle marks per unit area of the inorganic fibersheet (hereinafter referred to as needle mark density) is notparticularly limited, and the larger the needle mark density, the higherthe shear force, whereas the surface pressure decreases, and the smallerthe needle mark density, the larger the surface pressure, whereas theshear force decreases. Therefore, the needle mark density is preferablyto the extent that the shear force and the surface pressure are in goodbalance. The needle mark density may be, for example, 1.0 piece/cm² ormore and 50.0 pieces/cm² or less.

Here, the number of needle marks may be the number of white spotsprojected onto another surface of the inorganic fiber sheet when onesurface of the inorganic fiber sheet is exposed to visible light.Incidentally, the white spot may be confirmed regardless of whether theneedle mark is a through hole or a non-through hole.

The needle mark may be provided at equal intervals in plan view, and maybe provided at random. The average distance between two adjacent needlemarks may be, for example, 0.1 cm or more and 4 cm or less.

Also, the inorganic fiber sheet may be a papermaking sheet.

The average thickness of the inorganic fiber sheet is not particularlylimited, and may be appropriately set depending on the application, forexample.

The inorganic fiber sheet may be lengthy, and may be single sheet shape.Among them, the lengthy inorganic fiber sheet is preferable. Since thefiber diameter of the inorganic fiber in the inorganic fiber sheet maybe measured on-line, the present disclosure is useful for the lengthyinorganic fiber sheet.

Incidentally, since method for producing an inorganic fiber sheet isdescribed in “D. Method for producing inorganic fiber sheet” later,description thereof will be omitted here.

2. Sampling Section

The sampling section in the present disclosure is a section capable ofsampling a predetermined amount of the inorganic fiber in the entirearea of the inorganic fiber sheet.

Any sampling section will do as long as it is a section capable ofsampling a predetermined amount of the inorganic fiber in the entirearea of the inorganic fiber sheet, and for example, it may be a sectioncapable of sampling a predetermined amount of the inorganic fiber in theentire area in the in-plane direction of the inorganic fiber sheet; andit may be a section capable of sampling a predetermined amount of theinorganic fiber in the entire area in the in-plane direction and in thethickness direction of the inorganic fiber sheet. Among them, asdescribed above, a section capable of sampling a predetermined amount ofthe inorganic fiber representing the whole of the inorganic fiber sheetin the entire area of the inorganic fiber sheet is preferable. Thereason therefor is to improve the reliability of the fiber diameter.

Examples of the sampling section may include a section capable ofsampling a predetermined amount of the inorganic fiber in the entirearea of the inorganic fiber sheet without significantly impairing thephysical properties and appearance of the inorganic fiber sheet. Asdescribed above, since good appearance is required for the inorganicfiber sheet subjected to a needling treatment, the sampling section ispreferably a section not significantly impairing the appearance of theinorganic fiber sheet.

Also, when the inorganic fiber is sampled from the inorganic fiber sheetby the sampling section, it is only necessary to sample a predeterminedamount of the inorganic fiber in the entire area of the inorganic fibersheet, and for example, the inorganic fiber may be sampled from one sideof the inorganic fiber sheet, and the inorganic fiber may be sampledfrom both sides of the inorganic fiber sheet.

The sampling of the inorganic fiber may be carried out continuously andmay be carried out intermittently. Among them, the sampling of theinorganic fiber is preferably carried out continuously. The reasontherefor is to improve the reliability of the fiber diameter.

Also, in the sampling section, a predetermined amount of the inorganicfiber is sampled in the entire area of the inorganic fiber sheet. Atthis time, the amount of the inorganic fiber to be sampled may be equalto or more than an amount necessary for measuring the fiber diameter ofthe inorganic fiber. When more than the necessary amount of theinorganic fiber is sampled, the amount may be optimized to an amountnecessary for measurement by a reducing method.

Also, the inorganic fiber naturally dropped from the inorganic fibersheet may be included in the sampled inorganic fiber.

(1) Sample Collecting Section

The sampling section in the present disclosure may include a samplecollecting section configured to collect the inorganic fiber. The samplecollecting section includes, for example, a container with an opening.Specifically, as the sample collecting section, a container, forexample, placed on the upper side, the lower side, or the side surfaceof the inorganic fiber sheet, and has an opening on an upper side and/ora lower side and/or a side surface may be used; and if necessary, thesample transferring section described later may be used.

The sample collecting section may be placed on any of the upper, lower,and side surfaces of the inorganic fiber sheet.

Also, the sample collecting section may be placed so as to be in contactwith or proximity to the upper side or the lower side of the inorganicfiber sheet. Among them, when the sample transferring section describedlater is not used, the sample collecting section is preferably placed soas to be in contact with or proximity to the upper side or the lowerside of the inorganic fiber sheet. This is for preventing dust, floatingfiber, for example, in an atmosphere from mixing into the inorganicfiber when the inorganic fiber naturally dropped from the inorganicfiber sheet is collected. Particularly, when the sample transferringsection is not used, the sample collecting section is preferably placedso as to be proximity to the upper side or the lower side of theinorganic fiber sheet. The reason therefor is to suppress the appearanceof the inorganic fiber sheet from being impaired by the samplecollecting section being in contact with the inorganic fiber sheet. Inthis case, it is preferable that the sample collecting section is placedat a constant distance from the surface of the inorganic fiber sheet.

Also, as will be described later, when the sampling section in thepresent disclosure includes a pretreating section configured to assistthe sampling of the inorganic fiber, and uses feeding section configuredto feed a gas such as air or a liquid such as water to the inorganicfiber sheet as the pretreating section, the feeding section is a sectionconfigured to feed a gas or a liquid from one side or both sides of theinorganic fiber sheet, and the sample collecting section is a sectionconfigured to collect a fiber or a gas or a liquid including theinorganic fiber from the same side or the opposite to the side whereinthe feeding section of the inorganic fiber sheet is placed, or from bothsides of the inorganic fiber sheet.

When the feeding section is a gas feeding section, the sample collectingsection may be any section capable of collecting the inorganic fiberfrom either the same side as the side of the inorganic fiber sheetwherein the feeding section is placed (such as the upper side of theinorganic fiber sheet, when the feeding section is placed on the upperside of the inorganic fiber sheet), or the opposite side (such as thelower side of the inorganic fiber sheet, when the feeding section isplaced on the upper side of the inorganic fiber sheet), or both sides ofthe inorganic fiber sheet, and for example, a container for receivingthe inorganic fiber is used.

When the feeding section is a liquid feeding section, the samplecollecting section may be any section capable of collecting the liquidincluding the inorganic fiber, from either the same side of theinorganic fiber sheet as the side wherein the feeding section is placed(such as the upper side of the inorganic fiber sheet, when the feedingsection is placed on the upper side of the inorganic fiber sheet), orthe opposite side (such as the lower side of the inorganic fiber sheet,when the feeding section is placed on the upper side of the inorganicfiber sheet), or both sides of the inorganic fiber sheet, and forexample, a container for receiving the liquid including the inorganicfiber is used.

Also, as described later, when the sampling section in the presentdisclosure includes the pretreating section, and a section configured tobringing a plate-shaped material, a brush-shaped material, and acomb-shaped material (hereinafter, sometimes referred to as aplate-shaped material and the like) into substantially horizontallycontact with the inorganic fiber sheet surface, is used as thepretreating section, the sample collecting section is a sectionconfigured to collect the inorganic fiber generated by the contact ofthe plate-shaped material and the like with the inorganic fiber sheet.Among them, when a plate-shaped material and the like is placed on thelower side of the inorganic fiber sheet as a pretreating section, thesample collecting section may be a section configured to collect theinorganic fiber dropped by the contact of the plate-shaped material andthe like with the inorganic fiber sheet.

When a section configured to bringing a plate-shaped material and thelike into substantially horizontal contact with the inorganic fibersheet surface is used as the pretreating section, any section capable ofcollecting an inorganic fiber generated or dropped by the contact of theplate-shaped material and the like with the inorganic fiber sheet, maybe used as the sample collecting section, and for example, a containerreceiving an inorganic fiber, for example, is used. In this case, thesample collecting section may be used together with the sampletransferring section described later.

When a section configured to bring a plate-shaped material and the likeinto substantially horizontal contact with the inorganic fiber sheetsurface is used as the pretreating section, when a plate-shaped materialand the like is placed on the lower side of the inorganic fiber sheet,the sample collecting section is usually placed on the lower side of theinorganic fiber sheet. However, this is not the case when the sampletransferring section described later is used.

As will be described later, when the sampling section in the presentdisclosure includes a pretreating section, and when the vibrationsection configured to impart a vibration to the inorganic fiber sheet isused as the pretreating section, the sample collecting section may beany section capable of collecting the inorganic fiber dropped by thevibration, and for example, a container for receiving the inorganicfiber, for example, is used.

When the vibration section is used as the pretreating section, thesample collecting section is usually placed on the lower side of theinorganic fiber sheet. However, this is not the case when the sampletransferring section described later is used.

(2) Sample Transferring Section

The sampling section in the present disclosure may include a sampletransferring section placed on one side or both sides of the inorganicfiber sheet, and configured to transfer the inorganic fiber. Byincluding the sample transferring section, the amount of the inorganicfiber collected per unit time may be increased.

Examples of the sample transferring section may include: a suctioningsection; and physically conveyance section such as a section configuredto transfer the inorganic fiber in the vicinity of the inorganic fibersheet surface, by a conveyance device such as a belt conveyor and asection configured to transfer tweezers those have picked the inorganicfiber, and releasing the tweezers, thereby transferring the inorganicfiber to the sample collecting section.

The sample transferring section may be placed on one side of theinorganic fiber sheet, and may be placed on both sides of the inorganicfiber sheet. Also, when the sample transferring section is placed on oneside of the inorganic fiber sheet, it may be placed on the upper side ofthe inorganic fiber sheet, and may be placed on the lower side of theinorganic fiber sheet.

Also, the sample transferring section may be placed so as to be incontact with or proximity to one side or both sides of the inorganicfiber sheet. Among them, it is preferable that the sample transferringsection is placed so as to be proximity to one side or both sides of theinorganic fiber sheet. The reason therefor is to suppress the appearanceof the inorganic fiber sheet from being impaired by the contact of thesample transferring section with the inorganic fiber sheet. In thiscase, it is preferable that sample transferring section is placed at aconstant distance from one side or both sides of the inorganic fibersheet.

Also, as will be described later, when the sampling section in thepresent disclosure includes the pretreating section, and the feedingsection is used as the pretreating section, the sampling sectionpreferably includes a sample transferring section in order toefficiently collect the inorganic fiber.

When the feeding section is a gas feeding section, the sampletransferring section may be any section capable of transferring theinorganic fiber, and for example, the suctioning section and physicallyconveyance section may be used.

When the feeding section is a liquid feeding section, the sampletransferring section may be any section capable of transferring a liquidincluding the inorganic fiber, and for example, the suctioning sectionmay be used.

Also, as will be described later, when the sampling section in thepresent disclosure includes a pretreating section, and a sectionconfigured to bringing a plate-shaped material and the like intosubstantially horizontally contact with the inorganic fiber sheetsurface, is used as the pretreating section, the sampling sectionpreferably includes the sample transferring section.

When a section configured to bringing a plate-shaped material and thelike into substantially horizontal contact with the inorganic fibersheet surface is used as the pretreating section, the sampletransferring section may be any section capable of transferring theinorganic fiber, and for example, the suctioning section and physicallyconveyance section may be used.

When a section configured to bring a plate-shaped material and the likeinto substantially horizontal contact with the inorganic fiber sheetsurface is used as the pretreating section, the sample transferringsection is usually placed on the same side of the inorganic fiber sheet,as the side wherein the pretreating section is placed. Incidentally thearrangement of the sample transferring section is as described above.

Also, as will be described later, when the sampling section in thepresent disclosure includes a pretreating section configured to assistsin the sampling of the inorganic fiber, and the vibration section isused as the pretreating section, the sampling section preferablyincludes a sample transferring section in order to efficiently collectthe inorganic fiber.

When the vibration section is used as the pretreating section, thesample transferring section may be any section capable of transferringthe inorganic fiber, and for example, the suctioning section andphysically conveyance section may be used.

When the vibration section is used as the pretreating section, thesample transferring section is usually placed only on the lower side oron both sides of the inorganic fiber sheet. This is because, when thevibration section is used, it is necessary to collect the inorganicfiber dropped from the inorganic fiber sheet. Incidentally thearrangement of the sample transferring section is as described above.

(2-1) Suctioning Section

Among the above, a suctioning section is preferable as the sampletransferring section since it is simple.

The suctioning section is placed on one side or both sides of theinorganic fiber sheet, and is a section configured to suction theinorganic fiber.

The suctioning section may be placed on one side of the inorganic fibersheet, and may be placed on both sides of the inorganic fiber sheet.Also, when the suctioning section is placed on one side of the inorganicfiber sheet, it may be placed on the upper side of the inorganic fibersheet, and may be placed on the lower side of the inorganic fiber sheet.When the suctioning section is placed on the lower side of the inorganicfiber sheet, the distance between the inorganic fiber sheet and thesuctioning section may be set to a constant distance regardless of thethickness of the inorganic fiber sheet to be measured. Meanwhile, whenthe suctioning section is placed on the upper side of the inorganicfiber sheet, the collection of dust, for example, may be suppressed.

Also, the suctioning section is placed so as to be in contact with orproximity to one side or both sides of the inorganic fiber sheet. Inthis case, the suctioning section is preferably placed at a constantdistance from one side or both sides of the inorganic fiber sheet. Thereason therefor is to always collect the inorganic fiber at a constantsuctioning force, by keeping a constant distance in the thicknessdirection. Also, in this case, the constant distance may be zero, inother words, the suctioning section may be in contact with one side orboth sides of the inorganic fiber sheet. Among them, the suctioningsection is preferably placed so as to be proximity to one side or bothsides of the inorganic fiber sheet. The reason therefor is to suppressthe following defects due to the suctioning section being in contactwith the inorganic fiber sheet: the appearance of the inorganic fibersheet may be suppressed from being impaired; the physical properties maybe suppressed from being deteriorated due to the bend of the inorganicfiber sheet in the suctioning direction; and the possibility of foreignmatter such as dust being mixed by the suctioning section may bedecreased.

The output of the suctioning section is not particularly limited as longas it is capable of suctioning the inorganic fiber without significantlyimpairing the appearance of the inorganic fiber sheet.

The size of the suctioning section is not particularly limited as longas a predetermined amount of the inorganic fiber may be collected in theentire area of the inorganic fiber sheet, and the inorganic fiber may besuctioned without significantly impairing the appearance of theinorganic fiber sheet. For example, the width of the suctioning port ofthe suctioning section may be equal to or more than the width of theinorganic fiber sheet, and may be less than the width of the inorganicfiber sheet. Among them, the width of the suctioning port of thesuctioning section is preferably equal to or more than the width of theinorganic fiber sheet. The reason therefor is to collect the inorganicfiber uniformly in the width direction of the inorganic fiber sheet.Meanwhile, even when the width of the suctioning port of the suctioningsection is less than the width of the inorganic fiber sheet, apredetermined amount of the inorganic fiber may be collected in theentire area of the inorganic fiber sheet, by transferring the suctioningsection relative to the inorganic fiber sheet, as described later. Whenthe width of the suctioning port of the suctioning section is small, thesuctioning force may be increased, and collection of dust, for example,may be suppressed.

Here, for example, when a predetermined region of an end portion in thewidth direction of the inorganic fiber sheet is trimmed, the width ofthe suctioning port of the suctioning section being equal to or morethan the width of the inorganic fiber sheet includes an aspect whereinthe width of the suctioning port of the suctioning section is equal toor more than the width of the inorganic fiber sheet after trimming.

The suctioning section may be fixed at arbitrary position, and may bemovably placed at arbitrary position. When the suctioning section ismovably placed, the suctioning section may be movable in any of thewidth direction, longitudinal direction, and thickness direction of theinorganic fiber sheet. For example, when the suctioning section ismovable in the width direction of the inorganic fiber sheet, theinorganic fiber may be uniformly collected in the width direction of theinorganic fiber sheet. Specifically, it is only necessary to reciprocatethe suctioning section in the entire width direction of the inorganicfiber sheet. Also, for example, when the suctioning section is movablein the thickness direction of the inorganic fiber sheet, when thesuctioning section is placed on the upper side of the inorganic fibersheet, the distance between the inorganic fiber sheet and the suctioningsection may be set to a predetermined distance in accordance with thethickness of the inorganic fiber sheet to be measured.

Specifically, a dust collector may be used as the suctioning section.

The suction of the inorganic fiber may be carried out continuously, andmay be carried out intermittently. Among them, the suction of theinorganic fiber is preferably carried out continuously. The reasontherefor is to improve the reliability of the fiber diameter.

(3) Pretreating Section

The sampling section in the present disclosure may include a pretreatingsection configured to assist the sampling of the inorganic fiber.

The pretreating section is not particularly limited as long as it is asection configured to assisting the sampling of the inorganic fiber, andis preferably a section which does not significantly impair the physicalproperties and appearance of the inorganic fiber sheet. Specifically,the section is preferably a section wherein the vertical bundlescomposed of the inorganic fibers configured to bind fibers in thethickness direction, generated in the needling step, are less likely tobe damaged.

The pretreating section is placed on one side or both sides of theinorganic fiber sheet, and is preferably placed on the periphery of thesample collecting section. Also, for example, the pretreating sectionmay be placed on one side of the inorganic fiber sheet, and the samplecollecting section may be placed on the other side. Also, for example,the pretreating section may be placed on one side of the inorganic fibersheet, and the sample collecting section may be placed on the same sidethereof. Also, for example, the pretreating section may be placed onboth sides of the inorganic fiber sheet, and the sample collectingsection may be placed on the same side thereof.

The pretreating section is not particularly limited as long as it is asection configured to assist the sampling of the inorganic fiber, andexamples thereof may include a physically contactless section configuredto be physically contactless with the inorganic fiber sheet; and aphysically contacting section configured to be in physically contactwith the inorganic fiber sheet. Also, the physically contactless sectionand the physical contacting section may be used in a combination.

(3-1) Physically Contactless Section

The physically contactless section is not particularly limited as longas it is physically contactless with the inorganic fiber sheet, andassists the sampling of the inorganic fiber. Among the above, forexample, a feeding section configured to feed a gas such as air or aliquid such as water to the inorganic fiber sheet; and a sectionconfigured to feed air intermittently, for example, so as to vibrate theinorganic fiber sheet itself, are preferable. The physically contactingsection may be a single section described above, or may be a combinationthereof.

Incidentally, the section configured to feed air intermittently, forexample, so as to vibrate the inorganic fiber sheet itself is one of thevibration sections described later. The vibration section will bedescribed later.

(3-1-1) Feeding Section

The feeding section is a section configured to feed a gas such as air ora liquid such as water to the inorganic fiber sheet, from one side orboth sides of the inorganic fiber sheet.

As the gas, for example, air, vapor, carbon dioxide, and nitrogen may beused. Among them, air is preferable from the viewpoint of safety andbeing a gas at normal temperature and normal pressure. One kind of gasmay be used alone, and two or more kinds thereof may be mixed and used.

Also, the boiling point of the liquid is preferably 120° C. or less, andmore preferably in a range of 60° C. or more and 110° C. or less. Thereason therefor is to easily remove the liquid by setting the boilingpoint of the liquid in the above range. Meanwhile, when the boilingpoint is too high, it becomes difficult to completely remove the liquid.Also, when the boiling point is too low, the evaporation rate of theliquid becomes high, and it becomes difficult to sufficiently permeatethe liquid into the inorganic fiber sheet so that it may be difficult tocollect the liquid including the inorganic fiber.

The vapor pressure of the liquid at room temperature (25° C.) ispreferably relatively low, and specifically preferably 5 kPa or less.When the vapor pressure is too high, the evaporation rate of the liquidbecomes high, and it becomes difficult to sufficiently penetrate theliquid into the inorganic fiber sheet so that it may be difficult tocollect the liquid including the inorganic fiber.

The viscosity of the liquid is preferably relatively low, andspecifically, is preferably 3.5 mPa·s or less. When the viscosity of theliquid is low, the liquid tends to be impregnated into inorganic fibersheet, so that the liquid including the inorganic fiber may be easilycollected. Meanwhile, when the viscosity of the liquid is too high, itmay be difficult to sufficiently penetrate the liquid into the inorganicfiber sheet so that it may be difficult to collect the liquid includingthe inorganic fiber.

Here, the viscosity refers to a viscosity at 20° C., and is a valuemeasured using a rotary viscometer complying with JIS Z8803 (a methodfor measuring viscosity of a liquid).

The liquid is not particularly limited as long as it penetrates into theinorganic fiber sheet, and is preferably one which satisfies the aboveboiling point and viscosity. Examples of such a liquid may includewater, and lower alcohols such as ethanol. Among them, water ispreferable. Water is also suitable from an environmental point of view.As the water, for example, pure water may be used. One kind of theliquid may be used alone, and two or more kinds thereof may be mixed andused.

The gas feeding section is not particularly limited as long as the gasmay be uniformly fed to the inorganic fiber sheet without significantlyimpairing the appearance of the inorganic fiber sheet. Examples thereofmay include a section configured to blow a gas to the inorganic fibersheet. Also, the feed of gas may be carried out continuously, and may becarried out intermittently. Among them, the feed of the gas ispreferably carried out continuously. The reason therefor is to improvethe reliability of the fiber diameter.

The liquid feeding section is not particularly limited as long as theliquid may be uniformly fed to the inorganic fiber sheet withoutsignificantly impairing the appearance of the inorganic fiber sheet.Examples thereof may include a section configured to apply or spray aliquid to the inorganic fiber sheet. Among them, the liquid feedingsection is preferably a contactless method. The reason therefor is tosuppress the appearance of the inorganic fiber sheet from beingimpaired. Also, the feed of the liquid may be carried out continuously,and may be carried out intermittently. Among them, the feed of theliquid is preferably carried out continuously. The reason therefor is toimprove the reliability of the fiber diameter.

Also, as a gas or liquid feeding section, a fluid jet device configuredto blow a fluid such as a gas such as vapor and a liquid such as watermay be used, as long as the appearance of the inorganic fiber sheet isnot significantly impaired. Examples of the fluid jet device may includea steam jet device, and a water jet device. When the feeding section isa fluid jet device, it may also function as a needling sectionconfigured to carry out a needling treatment to the inorganic fiberprecursor sheet or the inorganic fiber sheet, to be described later.

The amount and pressure of the gas to be fed are not particularlylimited as long as the gas may be uniformly fed to the inorganic fibersheet without significantly impairing the appearance of the inorganicfiber sheet, and the inorganic fiber may be collected by the samplecollecting section, and are appropriately selected according to thethickness, for example, of the inorganic fiber sheet.

The amount and the pressure of the liquid to be fed are not particularlylimited as long as the liquid may be uniformly fed to the inorganicfiber sheet without significantly impairing the appearance of theinorganic fiber sheet, and the liquid including the inorganic fiber maybe collected by the sample collecting section, and is appropriatelyselected according to the thickness, for example, of the inorganic fibersheet.

(3-2) Physically Contacting Section

The physically contacting section is not particularly limited as long asit is a section configured to be in physically contact with theinorganic fiber sheet, and assist the sampling of the inorganic fiber.Examples of the physically contacting section may include a sectionconfigured to bring a plate-shaped material such as spatula usingmetals, resins, ceramics, and rubbers, for example, a brush-shapedmaterial such as a brush, and a comb-shaped material such as a comb intocontact with the inorganic fiber sheet surface substantiallyhorizontally; a section configured to pick the inorganic fiber up fromthe inorganic fiber sheet by a picking tool such as tweezers; and asection configured to vibrate the contacting site with the inorganicfiber sheet during conveyance. The physically contactless section may bea single section described above, and may be a combination of thesections described above.

Among them, the physically contacting section is preferably a sectionconfigured to bring a plate-shaped material such as spatula, abrush-shaped material such as a brush, and a comb-shaped material suchas a comb into contact with the inorganic fiber sheet surfacesubstantially horizontally; and a section configured to vibrate thecontacting site with the inorganic fiber sheet during conveyance.

Incidentally, a section configured to vibrate the contacting site withthe inorganic fiber sheet during conveyance is one of the vibrationsections described later. The vibration section will be described later.

(3-2-1) Section Configured to Bring Plate-Shaped Material and the LikeInto Contact with Inorganic Fiber Sheet Surface SubstantiallyHorizontally

A plate-shaped material such as spatula, a brush-shaped material such asa brush, and a comb-shaped material such as a comb (hereinafter, may bereferred to as a plate-shaped material and the like) scrapes theinorganic fiber on the surface and in the vicinity of the surface of theinorganic fiber sheet by bringing them into contact with the surface ofthe inorganic fiber sheet substantially horizontally.

The plate-shaped material and the like is not particularly limited aslong as it may collect the inorganic fiber by being in contact with thesurface of the inorganic fiber sheet; and a plate-shaped material suchas a spatula, a brush-shaped material such as a brush, and a comb-shapedmaterial such as a comb, for example, may be used.

Examples of the material of the plate-shaped material and the like mayinclude metal, resin, ceramic, and rubber.

When the inorganic fiber is collected using a plate-shaped material andthe like, it is preferable that a plate-shaped material and the like isbrought into substantially horizontally contact with the inorganic fibersheet so as not to impair the appearance of the inorganic fiber sheet.

The plate-shaped material and the like may be placed on the lower orupper side of the inorganic fiber sheet, and may be placed on both sidesthereof.

(3-3) Vibration Section

As the pretreating section, a vibration section may be used as thephysically contactless section, and a vibration section may be used asthe physical contacting section.

The vibration section is a section configured to impart a vibration tothe inorganic fiber sheet. The vibration section is preferable in thatthe inorganic fiber inside the inorganic fiber sheet may be moved to thesurface or in the vicinity of the surface of the inorganic fiber sheet.Also, the vibration section may be expected to have an effect of movingthe short fiber inside the inorganic fiber sheet to the surface or inthe vicinity of the surface of the inorganic fiber sheet so as to beeasily collected.

The vibration section is not particularly limited as long as it mayimpart a vibration to the inorganic fiber sheet without significantlyimpairing the appearance of the inorganic fiber sheet; and examplesthereof may include a section configured to vibrate the inorganic fibersheet itself by feeding air, for example, intermittently; and a sectionconfigured to vibrate a contacting site with the inorganic fiber sheetduring conveyance. Incidentally, as described above, the sectionconfigured to vibrate the inorganic fiber sheet itself by feeding air,for example, intermittently is included in the physically contactlesssection, and the section configured to vibrate a contacting site withthe inorganic fiber sheet during conveyance is included in thephysically contacting section.

Examples of the section configured to vibrate the inorganic fiber sheetitself by feeding air, for example, intermittently may include avibration generating section configured to generate a vibration; and ablower section configured to blow air to the inorganic fiber sheet.Specific examples of the vibration generating section may include anultrasonic vibration section, and a motor.

Example of the section configured to vibrate a contacting site with theinorganic fiber sheet during conveyance may include a shaking sectionconfigured to shake a contacting site with the inorganic fiber sheet,such as a conveyance device such as a conveyance roll or a conveyanceconveyor configured to convey the inorganic fiber sheet, and a substratewhich supports the inorganic fiber sheet; and a section configured tovibrate the inorganic fiber sheet by bringing a member different fromthe conveyance device into contact with the inorganic fiber sheet.Specifically, an ultrasonic vibration section, and a motor, for example,may be used as the shaking section. Also, as member different from theconveyance device described above, a pole, and a duster, for example,may be used.

The vibration may be imparted continuously or intermittently. Amongthem, the vibration is preferably imparted continuously. The reasontherefor is to improve the reliability of the fiber diameter.

The magnitude and frequency of the vibration are not particularlylimited as long as they are to the extent that the vibration may beimparted to the inorganic fiber sheet without significantly impairingthe appearance of the inorganic fiber sheet; and the inorganic fiber maybe collected by the vibration, and are appropriately selected.

The vibration section may be placed on one side or both sides of theinorganic fiber sheet. When the vibration section is used as thepretreating section, since the inorganic fiber may fall off from theinorganic fiber sheet surface due to the vibration caused by thevibration section, it is preferable that the vibration section is placedin the vicinity of or at the same position as the sample collectingsection. However, this is not the case when the sample transferringsection is used.

When the vibration section is a vibration generating section, thevibration generating section may be placed on either of the upper sideor the lower side of the inorganic fiber sheet.

Also, when the vibration section is a blower section, the blower sectionmay be placed on any of the upper side, the lower side, and the sidesurface of the inorganic fiber sheet. Among them, the blower section ispreferably placed on the upper side of the inorganic fiber sheet, and inthis case, it may also function as the feeding section.

(3-4) Preferable Embodiment of Pretreating Section

The feeding section and the vibration section are particularlypreferable as the pretreating section. This is because the inorganicfiber may be collected without significantly impairing the appearance ofthe inorganic fiber sheet. Also, when the sampling section includes thefeeding section or the vibration section as the pretreating section, thesampling section may be a section capable of collecting a predeterminedamount of the inorganic fiber in the entire area in the in-planedirection and the thickness direction of the inorganic fiber sheet. Inthis case, the reliability of the fiber diameter may be improved.

(4) Image Capturing Section

The sampling section in the present disclosure may include an imagecapturing section configured to capture an image of the inorganic fibercollected from the inorganic fiber sheet. Common measures for acquiringan image may be applied as the image capturing section; and examplesthereof may include a camera such as a CCD camera and a CMOS camera. Inthe image capturing section, for example, an image of an inorganic fibercollected by the sample collecting section may be acquired; and an imageof an inorganic fiber may be acquired not via the sample collectingsection. Therefore, when the sampling section includes the imagecapturing section, it may or may not include a sample collectingsection. Also, when the sampling section includes the image capturingsection, the measuring section described later may be a section whereinthe measurement is carried out by an image analysis.

(5) Preferable Embodiment of Sampling Section

As the sampling section, the sample transferring section or thepretreating section may be used alone, and the sample transferringsection and the pretreating section may be used in combination. Also,the sample transferring section may be a single section of each of thesections described above, and may be a combination of each of thesections described above. Similarly, the pretreating section may be asingle section of each of the sections described, and may be acombination of each of the sections described above.

Among them, the sampling section preferably includes the sampletransferring section and/or the pretreating section, and particularlypreferably includes the suctioning section as sample transferringsection and/or includes the feeding section or the vibration section asthe pretreating section. The reason therefore is that, in these samplingsections, the inorganic fiber may be collected without significantlyimpairing the appearance of the inorganic fiber sheet.

3. Measuring Section

The measuring section in the present disclosure is a section configuredto measure the fiber diameter of the sampled inorganic fiber.

The measuring section is not particularly limited as long as it is asection capable of measuring the fiber diameter of the inorganic fiber;and may be, for example, an automated fiber diameter measuring device,and may be a manual fiber diameter measuring device. The use of theautomated fiber diameter measuring device as the measuring section ispreferable in that it is easy to acquire the measured resultscontinuously.

Also, common measures for measuring the fiber diameter of an inorganicfiber may be applied as the measuring section; and for example, asection measuring with an optical microscope or a scanning electronmicroscope, a section measuring by an image analysis, and a sectionmeasuring by a laser diffraction may be used. Incidentally, a sectionconfigured to treat the inorganic fiber to be subjected to measurementinto an embodiment appropriate for the measurement according to themeasuring section, may be provided; and examples of such a section mayinclude a section configured to disperse the inorganic fiber into asolvent such as water, and a section configured to pulverize theinorganic fiber. Specifically, there is a treating process that complieswith COMMISSION REGULATION (EC) No. 761/2009.

The measurement of the fiber diameter of the inorganic fiber may becarried out continuously or intermittently.

After measuring the fiber diameter of the inorganic fiber by themeasuring section, whether the fiber diameter of the inorganic fiber iswithin a predetermined range set in advance, or not is confirmed.

4. Another Embodiment of Fiber Diameter Measuring Device

Another embodiment of the fiber diameter measuring device in the presentdisclosure is a fiber diameter measuring device configured to measure afiber diameter of an inorganic fiber in an inorganic fiber sheetincluding the inorganic fiber and subjected to a needling treatment, thedevice comprising, a sampling section capable of sampling apredetermined amount of the inorganic fiber in an entire area of theinorganic fiber sheet; and a measuring section configured to measure afiber diameter of the sampled inorganic fiber, and the sampling sectionincludes at least a sample collecting section configured to collect theinorganic fiber.

B. Inorganic Fiber Sheet Producing Device

Next, the inorganic fiber sheet producing device in the presentdisclosure will be described. The inorganic fiber sheet producing devicein the present disclosure is a device comprising the fiber diametermeasuring device described above.

FIG. 4 is a schematic view illustrating an example of an inorganic fibersheet producing device in the present disclosure. Inorganic fiber sheetproducing device 20 illustrated in FIG. 4 is an example of a producingdevice configured to produce a lengthy inorganic fiber sheet 1. Asillustrated in FIG. 4 , inorganic fiber sheet producing device 20comprises fiber diameter measuring device 10 including sampling section2 and measuring section 3. The fiber diameter measuring device 10 issimilar to the fiber diameter measuring device 10 illustrated in FIG. 1described above. Also, the inorganic fiber sheet producing device 20further comprises burning section 4 configured to burn inorganic fiberprecursor sheet 1 a including an inorganic fiber precursor continuously,on the upstream side of the fiber diameter measuring device 10.

In the inorganic fiber sheet producing device 20 illustrated in FIG. 4 ,a lengthy inorganic fiber precursor sheet 1 a and a lengthy inorganicfiber sheet 1 are conveyed by conveyance rolls 13, 11, and 12; andfirstly, the inorganic fiber precursor sheet 1 a is continuously burnedby the burning section 4 to obtain the inorganic fiber sheet 1. Then, inthe fiber diameter measuring device 10 including the sampling section 2and the measuring section 3, a predetermined amount of the inorganicfiber is sampled in the entire area of the inorganic fiber sheet 1, andthe fiber diameter of the sampled inorganic fiber is measured.

Incidentally, FIG. 4 is an example of a producing device configured tomeasure the fiber diameter of the inorganic fiber in a lengthy inorganicfiber sheet 1. However, although not illustrated in the figure, theinorganic fiber sheet producing device in the present disclosure may be,for example, a producing device including a cutting section configuredto cut the inorganic fiber sheet, between the burning section and thefiber diameter measuring device, and may be a producing deviceconfigured to measure a fiber diameter of an inorganic fiber in a singlesheet shaped inorganic fiber sheet.

According to the present disclosure, by comprising the fiber diametermeasuring device described above, the continuous safeness of the fiberdiameter of the inorganic fiber in the inorganic fiber sheet may beguaranteed, so that the reliability of the average fiber diameter andthe fiber diameter distribution, for example, of the measured inorganicfiber may be improved. Specifically, the average fiber diameter and thefiber diameter distribution, for example, of the inorganic fiber in theentire area of the lengthy inorganic fiber sheet may be guaranteed.Therefore, an inorganic fiber sheet with further improved safeness maybe provided.

Also, according to the present disclosure, by comprising the fiberdiameter measuring device described above, it is possible to measure thefiber diameter of the inorganic fiber in the inorganic fiber sheet, notonly after the production of the inorganic fiber sheet but also duringthe production of the inorganic fiber sheet. That is, the fiber diameterof the inorganic fiber in the inorganic fiber sheet may be measuredon-line. Therefore, the average fiber diameter and the fiber diameterdistribution of the inorganic fiber in the inorganic fiber sheet may becontrolled on-line. Also, the variation of the average fiber diameterand the fiber diameter distribution, for example, of the inorganic fiberand deviation from acceptable range may be checked on-line. Therefore,by feeding the result back to the production process, for example, ofthe inorganic fiber sheet, and controlling the production conditions,for example, of the inorganic fiber sheet, the average fiber diameter,and the fiber diameter distribution, for example, of the inorganic fibermay be kept in an acceptable range.

Also, according to the present disclosure, by comprising the fiberdiameter measuring device described above, an inorganic fiber sheet withgood appearance even after the measurement of the fiber diameter may beobtained.

Hereinafter, each configuration of the inorganic fiber sheet producingdevice in the present disclosure is described.

1. Fiber Diameter Measuring Device

The fiber diameter measuring device in the present disclosure has beendescribed in detail in “A. Fiber diameter measuring device” above; thus,the description herein is omitted.

2. Inorganic Fiber Sheet Producing Section

On the upstream side of the fiber diameter measuring device, theinorganic fiber sheet producing device in the present disclosure may beprovided with an inorganic fiber sheet producing section configured toproduce an inorganic fiber sheet.

The inorganic fiber sheet producing section is not particularly limitedas long as it is a section capable of producing an inorganic fibersheet.

The inorganic fiber sheet producing section may include, for example, asection configured to continuously produce a lengthy inorganic fibersheet. Among them, the inorganic fiber sheet producing sectionpreferably includes a burning section configured to continuously burnthe inorganic fiber precursor sheet including an inorganic fiberprecursor. This is because the fiber diameter distribution tends to varywhen the inorganic fiber sheet is continuously produced, and it isparticularly difficult to obtain a fiber diameter measuring samplerepresenting the inorganic fiber sheet.

Examples of the inorganic fiber sheet producing section may include afirst aspect including burning section configured to burn the inorganicfiber precursor sheet including an inorganic fiber precursor; and asecond aspect including a papermaking sheet producing section configuredto produce an inorganic fiber sheet which is a papermaking sheet.Hereinafter, each aspect will be described.

(1) First Aspect of Inorganic Fiber Sheet Producing Section

The first aspect of the inorganic fiber sheet producing section includesa burning section configured to burn the inorganic fiber precursor sheetincluding an inorganic fiber precursor.

(1-1) Burning Section

On the upstream side of the fiber diameter measuring device, theinorganic fiber sheet producing device in the present disclosure may beprovided with a burning section configured to burn the inorganic fiberprecursor sheet including the inorganic fiber precursor. Among them, theinorganic fiber sheet producing device in the present disclosurepreferably comprises a burning section configured to continuously burnthe inorganic fiber precursor sheet, including an inorganic fiberprecursor, on the upstream side of the fiber diameter measuring device.This is because the present disclosure is useful for producing a lengthyinorganic fiber sheet.

Here, continuously burning the inorganic fiber precursor sheet meansthat the lengthy inorganic fiber precursor sheet is burned whileconveyed.

The burning section is not particularly limited as long as it is asection capable of continuously burning the inorganic fiber precursorsheet; and a heating furnace, for example, may be used.

The burning temperature of the inorganic fiber precursor sheet may be,for example, 500° C. or more, preferably in a range of 1000° C. or moreand 1300° C. or less.

(1-2) Other Section

The first aspect of the inorganic fiber sheet producing section may beprovided with other section as needed, in addition to the burningsection described above.

The inorganic fiber sheet producing device in the present disclosure maybe provided with a needling section configured to carry out a needlingtreatment to the inorganic fiber precursor sheet, for example, on theupstream side or the downstream side of the burning section. In otherwords, the inorganic fiber precursor sheet may be one subjected to aneedling treatment. Among them, when the inorganic fiber sheet producingsection in the present aspect comprises a needling section, the needlingsection is preferably provided on the upstream side of the burningsection. The present disclosure is useful for an inorganic fiber sheetobtained by burning an inorganic fiber precursor sheet subjected to aneedling treatment.

Also, the inorganic fiber sheet producing device in the presentdisclosure may be provided with, for example, on the upstream side ofthe burning section and the needling section, a spinning sectionconfigured to spin a spinning solution to form an inorganic fiberprecursor; and an inorganic fiber precursor sheet forming sectionconfigured to integrate the inorganic fiber precursor to form aninorganic fiber precursor sheet, in this order from the upstream side.In the spinning section, a short fibrous inorganic fiber precursor maybe obtained.

Here, in the case of long fiber, it is easy to control the fiberdiameter at the spinning stage, and it is easy to ensure safeness, sincethe control of the fiber length is easy at the cutting or thepulverizing stage, whereas in the case of short fiber, it is difficultto control the fiber diameter as compared with the long fiber.

In the first aspect of the inorganic fiber sheet producing section, inthe spinning section, as described above, an inorganic fiber precursorin a short fibrous form is obtained. Therefore, it is difficult toguarantee the safeness of the inorganic fiber sheet obtained in thefirst aspect of the inorganic fiber sheet producing section unlessexamined, so that it is useful in the present disclosure.

(1-3) Inorganic Fiber Precursor Sheet

The inorganic fiber precursor sheet used in the present aspect is oneincluding an inorganic fiber precursor. As described above, theinorganic fiber precursor is preferably spun as a short fiber.

The inorganic fiber precursor sheet may be lengthy or single sheetshape. Among them, the inorganic fiber precursor sheet is preferablylengthy. This is because the present disclosure is suitable for alengthy inorganic fiber sheet.

When the inorganic fiber precursor sheet is one subjected to a needlingtreatment, it has a plurality of needle marks, that is, it has aplurality of recesses. The needle mark may be a through hole whichpenetrates through in the thickness direction of the inorganic fiberprecursor sheet, and may be a non-through hole which does not penetratethrough the sheet.

Incidentally the number of needle marks of the inorganic fiber precursorsheet may be the same as the number of needle marks of the inorganicfiber sheet described above.

The average thickness of the inorganic fiber precursor sheet is notparticularly limited, and may be appropriately set depending on theapplication, for example.

Incidentally, the method for producing an inorganic fiber precursorsheet will be described in “C. Method for producing inorganic fibersheet” later, and therefore, description thereof will be omitted here.

(2) Second Aspect of Inorganic Fiber Sheet Producing Section

On the upstream side of the fiber diameter measuring device, theinorganic fiber sheet producing device in the present disclosure may beprovided with a papermaking sheet producing section configured toproduce an inorganic fiber sheet which is a papermaking sheet.

The papermaking sheet producing section may include, for example, apapermaking section configured to make a slurry including an inorganicfiber, water, and a binder; and a drying section configured to dry thesheet obtained by the papermaking section.

Incidentally, the method for producing an inorganic fiber sheet which isa papermaking sheet will be described in “C. Method for producinginorganic fiber sheet” later, and therefore, description thereof will beomitted here.

The inorganic fiber sheet producing section in the present aspect may beprovided with a needling section configured to subject a needlingtreatment to the inorganic fiber sheet, if necessary, on the upstreamside of the papermaking sheet producing section.

(3) Other Aspects of Inorganic Fiber Sheet Producing Section

On the upstream side of the fiber diameter measuring device, theinorganic fiber sheet producing device in the present disclosure may beprovided with a section configured to produce an inorganic fiber sheet,and a needling section configured to carry out a needling treatment tothe inorganic fiber sheet. In other words, the inorganic fiber sheetproducing section may be provided with a needling section regardless ofwhich section produces the inorganic fiber sheet. The present disclosureis useful for an inorganic fiber sheet subjected to a needlingtreatment.

3. Other Section

The inorganic fiber sheet producing device in the present disclosure maybe provided with other section as needed, in addition to the fiberdiameter measuring device described above.

The inorganic fiber sheet producing device in the present disclosure maybe provided with, for example, a winding section configured to wind thelengthy inorganic fiber sheet into a roll-shaped manner, on thedownstream side of the fiber diameter measuring device. Alternatively,the inorganic fiber sheet producing device in the present disclosure mayinclude a cutting section configured to cut an inorganic fiber sheet,for example, between the burning section and the fiber diametermeasuring device.

The inorganic fiber sheet producing device in the present disclosure maybe provided with an impregnation section configured to impregnate abinder liquid into the inorganic fiber sheet; and a drying sectionconfigured to dry the binder liquid impregnated inorganic fiber sheetformed by impregnating inorganic fiber sheet with a binder liquid, forexample, on the downstream side of the fiber diameter measuring device.

C. Method for Measuring a Fiber Diameter

Next, a method for measuring a fiber diameter in the present disclosurewill be described. The method for measuring a fiber diameter in thepresent disclosure is a method for measuring a fiber diameter measuringa fiber diameter of an inorganic fiber in an inorganic fiber sheetincluding the inorganic fiber, the method comprising, a sampling step ofsampling the inorganic fiber from the inorganic fiber sheet by asampling method capable of sampling a predetermined amount of theinorganic fiber in an entire area of the inorganic fiber sheet; and ameasuring step of measuring the fiber diameter of the sampled inorganicfiber.

According to the present disclosure, since a predetermined amount of theinorganic fiber may be sampled in the entire area of the inorganic fibersheet in the sampling step, it is possible to improve the reliability ofthe fiber diameter of the measured inorganic fiber. Also, since theinorganic fiber sheet is not punched out or cut out for sampling, thefiber diameter of the inorganic fiber in the inorganic fiber sheet maybe measured on-line. Still more, since the appearance of the inorganicfiber sheet may be suppressed from being impaired by measurement of thefiber diameter, the inorganic fiber sheet may be used as a product evenafter measurement of the fiber diameter.

Hereinafter, each step in the method for measuring a fiber diameter inthe present disclosure will be described.

1. Sampling Step

The sampling step in the present disclosure is a step of sampling theinorganic fiber from the inorganic fiber sheet by a sampling methodcapable of sampling a predetermined amount of the inorganic fiber in anentire area of the inorganic fiber sheet.

A method of sampling the inorganic fiber is not particularly limited aslong as it is a method capable of sampling a predetermined amount of theinorganic fiber in the entire area of the inorganic fiber sheet, andexamples thereof may include a sampling method with the sampling sectiondescribed in the section “A. Fiber diameter measuring device, 2.Sampling section” above.

The inorganic fiber sheet subjected to the sampling step is oneincluding the inorganic fiber. Also, the inorganic fiber sheet subjectedto the sampling step is preferably subjected to a needling treatment.The inorganic fiber sheet may be the same as those described in thesection “A. Fiber diameter measuring device, 1. Inorganic fiber sheet”above.

2. Measuring Step

The measuring step in the present disclosure is a step of measuring thefiber diameter of the sampled inorganic fiber.

As a method for measuring the fiber diameter of the inorganic fiber, aknown method may be applied, and examples thereof may include themeasurement method according to measuring section described in thesection “A. Fiber diameter measuring device, 3. Measuring section”above.

The rest of the measuring step may be the same as those described in “A.Fiber diameter measuring device, 3. Measuring section” above.

3. Other Steps

In the method for measuring a fiber diameter in the present disclosure,it is preferable to carry out a step of removing dust, fiber, forexample, generated in the producing process of an inorganic fiber sheetand dust and fiber floating in the atmosphere, immediately before thesampling step.

D. Method for Producing Inorganic Fiber Sheet

Next, the method for producing an inorganic fiber sheet in the presentdisclosure will be described. The method for producing an inorganicfiber sheet in the present disclosure is a method for producingcomprising a sampling step of sampling an inorganic fiber from aninorganic fiber sheet by a sampling method capable of sampling apredetermined amount of the inorganic fiber in an entire area of theinorganic fiber sheet including the inorganic fiber; and a measuringstep of measuring the fiber diameter of the sampled inorganic fiber.

FIG. 4 is a schematic view illustrating an example of the method forproducing an inorganic fiber sheet in the present disclosure. FIG. 4 isan example of a method for producing wherein a fiber diameter of aninorganic fiber in a lengthy inorganic fiber sheet 1 is measured. Asillustrated in FIG. 4 , firstly, the lengthy inorganic fiber precursorsheet 1 a is conveyed with conveyance roll 13 to burning section 4; andat burning section 4, continuously conveyed inorganic fiber precursorsheet 1 a is burned to be inorganic fiber sheet 1. Then, whilecontinuously conveying the lengthy inorganic fiber sheet 1 withconveyance rolls 11 and 12, the inorganic fiber is suctioned from thelower side of the inorganic fiber sheet 1 being conveyed, by sampletransferring section 2 a (suctioning section) to collect the inorganicfiber. Then, the fiber diameter of the sampled inorganic fiber ismeasured by measuring section 3.

According to the present disclosure, since a predetermined amount of theinorganic fiber may be sampled in the entire area of the inorganic fibersheet in sampling step, the sampled inorganic fiber may be regarded asrepresenting the inorganic fiber in the inorganic fiber sheet.Therefore, the continuous safeness of the fiber diameter of theinorganic fiber in the inorganic fiber sheet may be guaranteed, so thatthe reliability of the average fiber diameter and the fiber diameterdistribution, for example, of the measured inorganic fiber may beimproved. Specifically, for a lengthy inorganic fiber sheet, the averagefiber diameter and the fiber diameter distribution, for example, of theinorganic fiber in the entire area of the lengthy inorganic fiber sheetmay be guaranteed. Therefore, an inorganic fiber sheet with furtherimproved safeness may be provided.

Also, according to the present disclosure, since the inorganic fiber issampled by a method capable of sampling a predetermined amount of theinorganic fiber in the entire area of the inorganic fiber sheet in thesampling step, the inorganic fiber sheet is not punched out or cut outfor sampling. Therefore, the fiber diameter of the inorganic fiber inthe inorganic fiber sheet may be measured, not only after the productionof the inorganic fiber sheet but also during the production of theinorganic fiber sheet. That is, the fiber diameter of the inorganicfiber in the inorganic fiber sheet may be measured on-line. Therefore,the average fiber diameter and the fiber diameter distribution, forexample, of the inorganic fiber in the inorganic fiber sheet may becontrolled on-line.

Also, according to the present disclosure, since the inorganic fiber issampled by a method capable of sampling a predetermined amount of theinorganic fiber in the entire area of the inorganic fiber sheet insampling step, the inorganic fiber sheet is not punched out or cut outfor sampling. Therefore, the appearance of the inorganic fiber sheet maybe suppressed from being impaired. Therefore, an inorganic fiber sheethaving good appearance even after the measurement of the fiber diametermay be obtained.

Hereinafter, each step in the method for producing an inorganic fibersheet in the present disclosure will be described. Incidentally, eachstep in the method for producing an inorganic fiber sheet in the presentdisclosure may be described by citing each step in a method forproducing an alumina fiber sheet which is an aspect of the inorganicfiber sheet in the present disclosure, as an example in some cases.

1. Inorganic Fiber Sheet Producing Step

The method for producing an inorganic fiber sheet in the presentdisclosure includes an inorganic fiber sheet producing step of producingan inorganic fiber sheet, prior to the sampling step. In the inorganicfiber sheet producing step, a method for producing an inorganic fibersheet is not particularly limited.

In the inorganic fiber sheet producing step, for example, a lengthyinorganic fiber sheet may be produced continuously. Among them, theinorganic fiber sheet producing step preferably includes a preparingstep of preparing an inorganic fiber precursor sheet including aninorganic fiber precursor; and a burning step of burning the inorganicfiber precursor sheet continuously to obtain the inorganic fiber sheet.This is because the fiber diameter distribution tends to vary wheninorganic fiber sheet is continuously produced, and it is particularlydifficult to obtain a fiber diameter measuring sample representing theinorganic fiber sheet.

Examples of the inorganic fiber sheet producing step may include a firstaspect including a preparing step of preparing an inorganic fiberprecursor sheet including an inorganic fiber precursor, and a burningstep of burning the inorganic fiber precursor sheet to obtain theinorganic fiber sheet; and a second aspect including a papermaking sheetproducing step of producing an inorganic fiber sheet which is apapermaking sheet. Hereinafter, each aspect will be described.

(1) First Aspect of Inorganic Fiber Sheet Producing Step

Prior to the sampling step, the method for producing an inorganic fibersheet in the present disclosure may include a preparing step ofpreparing an inorganic fiber precursor sheet including an inorganicfiber precursor; and a burning step of burning the inorganic fiberprecursor sheet to obtain the inorganic fiber sheet.

(1-1) Preparing Step

The preparing step in the present aspect is a step of preparing aninorganic fiber precursor sheet including an inorganic fiber precursor.In a method for producing an alumina fiber sheet which is an aspect ofthe inorganic fiber sheet in the present disclosure, the preparing stepis a step of preparing an alumina fiber precursor sheet including analumina fiber precursor.

As the method for producing an inorganic fiber precursor sheet, a knownmethod may be applied, and is not particularly limited. For example, thepreparing step may include a preparing step of preparing a spinningsolution; a spinning step of forming an inorganic fiber precursor byspinning the spinning solution; and an inorganic fiber precursor sheetforming step of forming an inorganic fiber precursor sheet byintegrating the inorganic fiber precursor. In the spinning step, forexample, a blowing method, and a spinning method, for example, may beused. Also, in the spinning step, a short fibrous inorganic fiberprecursor may be obtained.

Here, as described above, in the case of short fiber, it is difficult tocontrol the fiber diameter as compared with a long fiber. In the firstaspect of the inorganic fiber sheet producing step, in the spinningstep, as described above, an inorganic fiber precursor in a shortfibrous form is obtained. Therefore, it is difficult to guarantee thesafeness of the inorganic fiber sheet obtained in the first aspect ofthe inorganic fiber sheet producing step unless examined, so that it isuseful in the present disclosure.

As the method for producing an alumina fiber precursor sheet, a knownmethod may be applied, and is not particularly limited. Examples thereofmay include a method wherein a spinning solution including an aluminumcompound is prepared, the spinning solution is spun to form an aluminafiber precursor, the alumina fiber precursor is integrated to form analumina fiber precursor sheet, and a needling treatment is carried outto the alumina fiber precursor sheet.

The preparation of the spinning solution may be carried out according toa conventional method. The spinning solution, for example, may beprepared by adding a silicon compound to an aqueous basic aluminumchloride solution prepared by dissolving aluminum in hydrochloric acid.As the silicon compound, a silica sol is suitably used, and awater-soluble silicon compound such as tetraethylsilicate and awater-soluble siloxane derivative may be used.

In the spinning solution, the ratio of aluminum and silicon ispreferably in a range of 60:40 to 98:2 in terms of Al₂O₃/SiO₂ massratio, more preferably in a range of 65:35 to 95:5, and particularlypreferably in a range of 70:30 to 80:20. When the silicon component istoo much, fiberization is easy, but heat resistance may be remarkablylowered. Meanwhile, when the silicon component is too low, the fiber maybe easily embrittled.

Also, in order to improve spinnability, the spinning solution preferablyincludes a spinning auxiliary agent. Examples of the spinning auxiliaryagent may include water-soluble organic polymers such as polyvinylalcohol, polyethylene glycol, polyacrylamide, starch, and cellulosederivatives.

The spinning solution may be prepared, for example, by adding a siliconcompound and an organic polymer to an aqueous basic aluminum chloridesolution, and concentrating thereof as appropriate. The viscosity of thespinning solution at ordinary temperature may be, for example,approximately 10 poise or more and 100 poise or less.

The formation of the alumina fiber precursor from the spinning solutionmay be carried out according to a conventional method. Examples of theformation of an alumina fiber precursor from a spinning solution mayinclude a blowing method wherein a spinning solution is supplied into ahigh speed spinning air stream. As the nozzle for the blowing method,either one of the following two types may be used: a type wherein aspinning solution nozzle is installed in an air flow nozzle configuredto generate a spinning air stream; and a type wherein a spinningsolution nozzle is installed so as to supply the spinning solution fromthe outside of the spinning air stream. When spinning by the blowingmethod, for example, it is possible to use a method wherein an endlessbelt made of a wire mesh is installed so as to be substantiallyperpendicular to the spinning air stream, and while rotating the endlessbelt, a formed spinning air stream including an alumina fiber precursoris bombarded thereto. The alumina fiber precursor formed by thisspinning has a diameter of usually several pm, and a length of severaltens of mm to several hundreds of mm.

By integrating the alumina fiber precursor, an alumina fiber precursorsheet may be obtained. In producing an alumina fiber precursor sheet, analumina fiber precursor may be integrated to form a single layer sheet,and a thin layer sheet obtained by integrating an alumina fiberprecursor may be stacked.

The method for stacking the thin-layer sheet is not particularlylimited. For example, a method for producing a stacked sheet includingalumina fiber precursors, disclosed in JP-A No. 2000-80547 may beapplied. Specifically, a method for producing a stacked sheet includingalumina fiber precursor may be applied, wherein an alumina fiberprecursor is deposited on an integrating device to form a thin sheet ofalumina fiber precursor; the thin sheet is continuously taken out fromthe integrating device and forwarded to a folding device; folded to apredetermined width and stacked while continuously transferring in adirection perpendicular to the folding direction. In this method forproducing a stacked sheet including alumina fiber precursor, the thinsheet is continuously taken out from the integrating device, and iscontinuously transferred transversely to the folding direction whilebeing folded and stacked in the transferring direction of the thinsheet. Therefore, the width to be folded is equal to the width of thestacked sheet to be formed. Thus, both end portions in the widthdirection of the thin sheet is dispersed in the stacked sheet to beformed, so that the weight of the stacked sheet per unit area becomeseven over the entire stacked sheet. Such a method for producing astacked sheet including an alumina fiber precursor is one of a producingmethod wherein a sheet shape is formed after going through a stack byzigzag foldings.

Incidentally, the needling treatment will be described later.

(1-2) Burning Step

The burning step in the present aspect is a step of burning an inorganicfiber precursor sheet. The burning step is preferably a step ofcontinuously burning the inorganic fiber precursor sheet to obtain aninorganic fiber sheet.

The burning of the inorganic fiber precursor sheet may be carried outaccording to a conventional method. Incidentally, the burningtemperature is the same as that described in the section of “B.Inorganic fiber sheet producing device” above.

(1-3) Needling Step

In the present aspect, the method for producing an inorganic fiber sheetmay include a needling step of subjecting a needling treatment to theinorganic fiber precursor sheet, before or after the burning step. Thisis because the present disclosure is suitable for an inorganic fibersheet subjected to a needling treatment. Among them, when the inorganicfiber sheet producing step in the present aspect includes a needlingstep, the needling step is preferably included prior to the burningstep. The present disclosure is useful for an inorganic fiber sheetobtained by burning an inorganic fiber precursor sheet subjected to aneedling treatment.

By subjecting a needling treatment to the inorganic fiber precursorsheet, an inorganic fiber precursor sheet having high mechanicalstrength wherein the inorganic fiber precursor is also oriented in thethickness direction of the inorganic fiber precursor sheet, may beobtained.

For the needling treatment, a known method may be applied, and is notparticularly limited. For example, it may be similar to the needlingtreatment disclosed in WO 2016/152795.

The needling hole density may be, for example, 1 hole/cm² or more and 50holes/cm² or less. Generally, the greater the number of needling holes,the greater the bulk density and peeling strength of the resultinginorganic fiber precursor sheet.

(2) Second Aspect of Inorganic Fiber Sheet Producing Step

The method for producing an inorganic fiber sheet in the presentdisclosure may include a papermaking sheet producing step of producingan inorganic fiber sheet which is a papermaking sheet, prior to thesampling step.

The inorganic fiber sheet which is a papermaking sheeting may beproduced by a known method. The papermaking sheet producing step mayinclude, for example, a papermaking step of making a slurry including aninorganic fiber, water, and a binder; and a drying step of drying thesheet obtained in the papermaking step. Also, prior to the papermakingstep, the papermaking sheet producing step may include a defibratingstep of defibrating an inorganic fiber; and a slurry preparing step ofpreparing a slurry including the defibrated inorganic fiber as theinorganic fiber. For each step, a known method may be applied.

The inorganic fiber included in the slurry may be, for example, thatobtained by spinning long fiber and cutting or pulverizing thereof intoshort fiber; and may be that spun as short fiber. Among them, theinorganic fiber is preferably that was spun as short fiber. Here, asdescribed above, in the case of short fiber, it is difficult to controlthe fiber diameter as compared with the long fiber. Therefore, thepresent disclosure is suitable for an inorganic fiber spun as a shortfiber, which is difficult to guarantee the safeness unless examined.

The inorganic fiber sheet producing step in the present aspect mayinclude, as necessary, after the papermaking sheet producing step, aneedling step of subjecting a needling treatment to the inorganic fibersheet.

(3) Other Aspects of Inorganic Fiber Sheet Producing Step

Prior to the sampling step, the method for producing an inorganic fibersheet in the present disclosure may include a needling step ofsubjecting a needling treatment to the inorganic fiber sheet. In otherwords, the inorganic fiber sheet producing step may include the needlingstep regardless how an inorganic fiber sheet is produced. The presentdisclosure is useful for an inorganic fiber sheet subjected to aneedling treatment.

2. Sampling Step

The sampling step in the present disclosure is an inorganic step ofsampling the inorganic fiber from the inorganic fiber sheet by asampling method capable of sampling a predetermined amount of theinorganic fiber in an entire area of the inorganic fiber sheet.

A method for sampling the inorganic fiber is not particularly limited aslong as it is a method capable of sampling a predetermined amount of theinorganic fiber in the entire area of the inorganic fiber sheet, andexamples thereof may include a sampling method according to the samplingsection described in the section “A. Fiber diameter measuring device, 2.Sampling section” above.

In the present disclosure, the burning step and the sampling step arepreferably carried out continuously. The reason therefor is to samplethe inorganic fiber to be subjected to the measurement of the fiberdiameter, from the inorganic fiber sheet, on-line.

The inorganic fiber sheet to be subjected to the sampling step ispreferably one subjected to a needling treatment. By carrying out theneedling step, an inorganic fiber sheet subjected to a needlingtreatment may be obtained.

3. Measuring Step

The measuring step in the present disclosure is a step of measuring thefiber diameter of the sampled inorganic fiber.

As a method for measuring the fiber diameter of an inorganic fiber, aknown method may be applied, and examples thereof may include ameasurement method according to the measuring section described in thesection “A. Fiber diameter measuring device, 3. Measuring section”above.

Incidentally, the rest of the measuring step may be the same as thosedescribed in “A. Fiber diameter measuring device, 3. Measuring section”above.

In the present disclosure, the burning step, the sampling step, and themeasuring step are preferably carried out continuously. The reasontherefor is to measure the fiber diameter of the inorganic fiber in theinorganic fiber sheet on-line.

4. Feedback and Control

In the present disclosure, when the fiber diameter measured in themeasuring step is out of a previously set predetermined range, a resultthereof may be fed back, and producing conditions of the inorganic fiberprecursor sheet and/or burning conditions in the burning step may becontrolled so that the fiber diameter is in the predetermined range.Variation of the average fiber diameter and the fiber diameterdistribution of the inorganic fiber and deviation from acceptable rangemay be checked on-line. Therefore, by feeding the result back, andcontrolling the producing conditions of the inorganic fiber precursorsheet, and/or he burning conditions in the burning step, the averagefiber diameter and the fiber diameter distribution of the inorganicfiber may be kept in a predetermined range.

When the measured fiber diameter is out of a previously setpredetermined range, the result is fed back to control the producingconditions of the inorganic fiber precursor sheet and/or the burningconditions in the burning step so that the fiber diameter is in thepredetermined range. Meanwhile, when the measured fiber diameter is inthe predetermined range, the current producing conditions of theinorganic fiber precursor sheet and the burning conditions in theburning step are maintained.

The previously set predetermined range of the fiber diameter is, forexample, a range of value appropriately set according to thespecifications, for example, of the inorganic fiber sheet.

Specifically, whether the average fiber diameter, the standard deviationof the fiber diameter distribution, the minimum fiber diameter, and themaximum fiber diameter, for example, satisfy the specifications or not;and whether a target range is met or not, are confirmed. Alternatively,whether there is a singular point in the fiber diameter (such aspresence or absence of the fiber having a fiber diameter of 3 μm orless) or not, is confirmed.

A method for controlling the producing conditions of the inorganic fiberprecursor sheet and/or the burning conditions in the burning step inorder to adjust the fiber diameter may be appropriately set depending onwhether the fiber diameter satisfies the predetermined range or not.

Examples of the method for controlling the producing conditions of theinorganic fiber precursor sheet in order to adjust the fiber diametermay include a control of the preparing conditions of a spinningsolution, and a control of the spinning conditions. Examples of themethod for controlling the preparing conditions of the spinning solutionin order to adjust the fiber diameter may include a control of theviscosity of the spinning solution.

Also, examples of the method for controlling the burning conditions inthe burning step in order to adjust the fiber diameter may include acontrol of the burning temperature.

The feedback and the control may be carried out automatically ormanually.

5. Other Steps

In addition to the steps described above, the method for producing aninorganic fiber sheet in the present disclosure may include other steps,as necessary.

In the method for producing an inorganic fiber sheet in the presentdisclosure, prior to the sampling step, it is preferable to carry out astep of removing floating fiber and dust, for example, deposited and/oradhered to the inorganic fiber sheet during each of the steps describedabove and from the atmosphere, so that floating fiber and dust, forexample, deposited and/or adhered to the inorganic fiber sheet duringeach of the steps described above and from the atmosphere does notaffect the result of the fiber diameter measurement.

After the measuring step, the method for producing an inorganic fibersheet in the present disclosure may include, for example, a winding stepof winding the lengthy inorganic fiber sheet into a roll-shaped manner.Alternatively, between the burning step and the measuring step, themethod for producing an inorganic fiber sheet in the present disclosuremay include, for example, a cutting step of cutting the inorganic fibersheet.

After the measuring step, for example, the method for producing analumina fiber sheet which is an aspect of the inorganic fiber sheet inthe present disclosure may include an impregnation step of impregnatinga binder liquid into the alumina fiber sheet; and a drying step ofdrying the binder liquid impregnated alumina fiber sheet formed byimpregnating the alumina fiber sheet with the binder liquid.

6. Another Embodiment of Method for Producing Inorganic Fiber Sheet

Another embodiment of the method for producing an inorganic fiber sheetin the present disclosure comprises a preparing step of preparing aninorganic fiber precursor sheet including an inorganic fiber precursorand subjected to a needling treatment; a burning step of burning theinorganic fiber precursor sheet continuously to obtain an inorganicfiber sheet including an inorganic fiber and subjected to a needlingtreatment; sampling step of sampling an inorganic fiber from aninorganic fiber sheet by a sampling method capable of sampling apredetermined amount of the inorganic fiber in an entire area of theinorganic fiber sheet; and a measuring step of measuring the fiberdiameter of the sampled inorganic fiber.

Incidentally, the present disclosure is not limited to the embodiments.The embodiments are exemplification, and any other variations areintended to be included in the technical scope of the present disclosureif they have substantially the same constitution as the technical ideadescribed in the claim of the present disclosure and offer similaroperation and effect thereto.

EXAMPLES

The present disclosure is hereinafter explained in further details withreference to Example and Reference Examples.

Example 1

The raw fabric of a lengthy crystalline alumina/silica fiber sheet(Maftec (registered trade mark) from Mitsubishi Chemical Corporation)with 2400 gsm, a width of 150 mm and a length of 500 mm was prepared,and an ultrasonic dry cleaner for web (HG Cleaner VUV-HGv-130 fromShinko Co., Ltd.) was used as a nozzle head, and the inorganic fiber wascollected at a suction quantity of 500 L/min while discharging thecompressed air of 0.3 MPa. Incidentally, a nozzle head was placed on theupper side of the crystalline alumina/silica fiber sheet, and a feedrate of the crystalline alumina/silica fiber sheet in this case was setto 500 mm/min, and a PTFE membrane filter (Omnipore from Merck KGaA)with a pore diameter of 1 μm was used as a filter for collecting aninorganic fiber. The amount of the collected inorganic fiber was 0.05 g.

Next, with respect to the collected inorganic fiber, the collectedinorganic fiber was treated in a manner complying with the COMMISSIONREGULATION (EC) No 761/2009, and the diameter of approximately 300inorganic fibers was measured using an optical microscope.

Reference Example 1

The crystalline alumina/silica fiber sheet after collecting theinorganic fiber in Example 1 was punched out at six places with a corkborer of 25 mm φ uniformly in the width direction of the alumina/silicafiber sheet complying with COMMISSION REGULATION (EC) No 761/2009, andthe six test pieces were dispersed into 300 mL of water to obtain astock solution of a representative sample in the width direction(widthwise representative sample). Then, in the same manner as in thepreparing procedure of the stock solution of the widthwiserepresentative sample described above, a stock solution of a widthwiserepresentative sample was prepared in every 100 mm in the longitudinaldirection, and the stock solution of a widthwise representative sampleat 5 locations was obtained on the alumina/silica fiber sheet, bysumming up with the stock solution of the widthwise representativesample described above.

Then, after sufficiently stirring the stock solution of the obtainedwidthwise representative sample, 50 mL of the sample was taken out intoan empty container, 250 mL of water was added, and sufficiently stirredto obtain a dilution solution of the widthwise representative sample.The obtaining procedure of the dilution solution was carried out for allof the stock solutions of the 5 widthwise representative samplesdescribed above to prepare respective dilution solutions.

Then, by measuring the dilution solution of each widthwiserepresentative sample using an optical microscope, the diameter ofapproximately 300 inorganic fibers of the widthwise representativesamples was measured. Each widthwise representative sample was numberedfrom 1 to 5 in order from one side in the arbitrary longitudinaldirection, and the measured values were distinguished from each other.

Reference Example 2

From each dilution solution of each widthwise representative sampleprepared in Reference Example 1, 60 mL each was taken out, mixed in anempty container, and sufficiently stirred, thereby obtaining a 300 mLalumina/silica fiber dispersion. Since the alumina/silica fiberdispersion is a mixed liquid of each widthwise representative sample, itmay be regarded as one of the representative samples of alumina/silicafiber sheet. With respect to the alumina/silica fiber dispersion, thediameter of approximately 300 inorganic fibers representing thealumina/silica fiber sheet was measured using an optical microscope.

Reference Example 3

From each of the widthwise representative sample stock solutionsprepared in Reference Example 1, 10 mL each was taken out, mixed with250 mL of water in an empty container, and sufficiently stirred. Therebyobtaining a 300 mL alumina/silica fiber dispersion solution. Since thealumina/silica fiber dispersion solution was a mixed liquid of eachwidthwise representative sample, it may be regarded as one of therepresentative samples of the alumina/silica fiber sheet. With respectto the alumina/silica fiber dispersion solution, the diameter ofapproximately 300 inorganic fibers representing the alumina/silica fibersheet was measured using an optical microscope.

TABLE 1 Average Number of fiber Detected number of measured diameterfibers with diameter fibers (μm) of less than 3.0 μm Example 1 339 6.480 Reference Widthwise 332 6.13 0 Ex. 1 representative 1 Widthwise 3296.29 0 representative 2 Widthwise 341 6.54 0 representative 3 Widthwise334 6.32 0 representative 4 Widthwise 332 6.27 0 representative 5Widthwise — 6.34 0 representative average Reference Ex. 2 330 6.43 0Reference Ex. 3 338 6.24 0

[Evaluation]

Table 1 and FIG. 5 show the measurement results of the number averagefiber diameter and the detected number of fibers with diameter of lessthan 3.0 μm in Example 1 and Reference Examples 1 to 3. The plots ofreference example 1 shown in FIG. 5 are: widthwise representative 1,widthwise representative 2, widthwise representative 3, widthwiserepresentative 4, and widthwise representative 5 shown in Table 1,respectively, in order from the left. Also, when the standard deviationcalculated from the five points in Reference Example 1 is regarded as σ(sigma), the dashed line indicates the average value ±σ, the one-dotchain indicates the average value ±2σ, long two-dot chain indicates theaverage value ±3σ. The average fiber diameter in Example 1 was presentin the variation of the average fiber diameter of the five samples inReference Example 1, which are widthwise representative samples (sinceReference Example 1 was representative in the widthwise direction insamples respectively prepared from the same crystalline alumina/silicafiber sheet, the probability density of each value is considered tofollow a normal distribution, and the variation is within the averagevalue ±3σ), which indicates a value close to the average fiber diametersin Reference Examples 2 and 3, which are representative samples of thealumina/silica fiber sheets. From these results, it is found that themethod for measuring a fiber diameter disclosed in the presentdisclosure was capable of obtaining the same results as a conventionalmethod for measuring a fiber diameter offline complying with COMMISSIONREGULATION (EC) No 761/2009.

REFERENCE SIGNS LIST

1: inorganic fiber sheet

1 a: inorganic fiber precursor sheet

2: sampling section

2 a: sample transferring section

2 b: feeding section

2 c: sample collecting section

2 d: vibration section

3: measuring section

4: burning section

10: fiber diameter measuring device

11, 12, 13: conveyance roll

20: inorganic fiber sheet producing device

1-20. (canceled)
 21. A fiber diameter measuring device configured tomeasure a fiber diameter of an inorganic fiber in an inorganic fibersheet including the inorganic fiber, the device comprising, a samplingsection capable of sampling a predetermined amount of the inorganicfiber in an entire area of the inorganic fiber sheet; and a measuringsection configured to measure a fiber diameter of the sampled inorganicfiber.
 22. The fiber diameter measuring device according to claim 21,wherein the sampling section includes a sample transferring sectionplaced on one side or both sides of the inorganic fiber sheet, andconfigured to transfer the inorganic fiber.
 23. The fiber diametermeasuring device according to claim 22, wherein the sample transferringsection is a suctioning section configured to suction the inorganicfiber.
 24. The fiber diameter measuring device according to claim 21,wherein the sampling section includes a pretreating section configuredto assist the sampling of the inorganic fiber.
 25. The fiber diametermeasuring device according to claim 24, wherein the pretreating sectionis a physically contactless section configured to be physicallycontactless with the inorganic fiber sheet.
 26. The fiber diametermeasuring device according to claim 25, wherein the physicallycontactless section is a feeding section configured to feed a gas or aliquid to the inorganic fiber sheet, from one side or both sides of theinorganic fiber sheet.
 27. The fiber diameter measuring device accordingto claim 24, wherein the pretreating section is a physically contactingsection configured to be in physically contact with the inorganic fibersheet.
 28. The fiber diameter measuring device according to claim 24,wherein, as the pretreating section, the sampling section includes avibration section configured to impart a vibration to the inorganicfiber sheet.
 29. The fiber diameter measuring device according to claim21, wherein the sampling section includes a sample collecting sectionconfigured to collect the inorganic fiber.
 30. An inorganic fiber sheetproducing device comprising the fiber diameter measuring deviceaccording to claim
 21. 31. The inorganic fiber sheet producing deviceaccording to claim 30, wherein a burning section configured to burn aninorganic fiber precursor sheet including an inorganic fiber precursorcontinuously, is provided on an upstream side of the fiber diametermeasuring device.
 32. A method for measuring a fiber diameter measuringa fiber diameter of an inorganic fiber in an inorganic fiber sheetincluding the inorganic fiber, the method comprising, a sampling step ofsampling the inorganic fiber from the inorganic fiber sheet by asampling method capable of sampling a predetermined amount of theinorganic fiber in an entire area of the inorganic fiber sheet; and ameasuring step of measuring the fiber diameter of the sampled inorganicfiber.
 33. The method for measuring a fiber diameter according to claim32, wherein, in the sampling step, the inorganic fiber is transferred bya sample transferring section placed on one side or both sides of theinorganic fiber sheet, and configured to transfer the inorganic fiber.34. The method for measuring a fiber diameter according to claim 32,wherein, in the sampling step, the sampling of the inorganic fiber isassisted by a pretreating section configured to assist the sampling ofthe inorganic fiber.
 35. A method for producing an inorganic fibersheet, the method comprising, a sampling step of sampling an inorganicfiber from an inorganic fiber sheet by a sampling method capable ofsampling a predetermined amount of the inorganic fiber in an entire areaof the inorganic fiber sheet including the inorganic fiber; and ameasuring step of measuring the fiber diameter of the sampled inorganicfiber.
 36. The method for producing an inorganic fiber sheet accordingto claim 35, wherein, in the sampling step, the inorganic fiber istransferred by a sample transferring section placed on one side or bothsides of the inorganic fiber sheet, and configured to transfer theinorganic fiber.
 37. The method for producing an inorganic fiber sheetaccording to claim 35, wherein, in the sampling step, the sampling ofthe inorganic fiber is assisted by a pretreating section configured toassist the sampling of the inorganic fiber.
 38. The method for producingan inorganic fiber sheet according to claim 35, wherein, prior to thesampling step, the method comprises a preparing step of preparing aninorganic fiber precursor sheet including an inorganic fiber precursor;and a burning step of burning the inorganic fiber precursor sheetcontinuously to obtain the inorganic fiber sheet.
 39. The method forproducing an inorganic fiber sheet according to claim 38, wherein, whenthe fiber diameter measured in the measuring step is out of a previouslyset predetermined range, a result thereof is fed back, and a producingcondition of the inorganic fiber precursor sheet and/or a burningcondition in the burning step is controlled so that the fiber diameteris in the predetermined range.
 40. The method for producing an inorganicfiber sheet according to claim 35, wherein the inorganic fiber sheetsubjected to the sampling step is an inorganic fiber sheet subjected toa needling treatment.